xref: /freebsd/contrib/llvm-project/libcxx/include/algorithm (revision dd41de95a84d979615a2ef11df6850622bf6184e)
1// -*- C++ -*-
2//===-------------------------- algorithm ---------------------------------===//
3//
4// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
5// See https://llvm.org/LICENSE.txt for license information.
6// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
7//
8//===----------------------------------------------------------------------===//
9
10#ifndef _LIBCPP_ALGORITHM
11#define _LIBCPP_ALGORITHM
12
13/*
14    algorithm synopsis
15
16#include <initializer_list>
17
18namespace std
19{
20
21template <class InputIterator, class Predicate>
22    constexpr bool     // constexpr in C++20
23    all_of(InputIterator first, InputIterator last, Predicate pred);
24
25template <class InputIterator, class Predicate>
26    constexpr bool     // constexpr in C++20
27    any_of(InputIterator first, InputIterator last, Predicate pred);
28
29template <class InputIterator, class Predicate>
30    constexpr bool     // constexpr in C++20
31    none_of(InputIterator first, InputIterator last, Predicate pred);
32
33template <class InputIterator, class Function>
34    constexpr Function          // constexpr in C++20
35    for_each(InputIterator first, InputIterator last, Function f);
36
37template<class InputIterator, class Size, class Function>
38    constexpr InputIterator     // constexpr in C++20
39    for_each_n(InputIterator first, Size n, Function f); // C++17
40
41template <class InputIterator, class T>
42    constexpr InputIterator     // constexpr in C++20
43    find(InputIterator first, InputIterator last, const T& value);
44
45template <class InputIterator, class Predicate>
46    constexpr InputIterator     // constexpr in C++20
47    find_if(InputIterator first, InputIterator last, Predicate pred);
48
49template<class InputIterator, class Predicate>
50    InputIterator               // constexpr in C++20
51    find_if_not(InputIterator first, InputIterator last, Predicate pred);
52
53template <class ForwardIterator1, class ForwardIterator2>
54    ForwardIterator1            // constexpr in C++20
55    find_end(ForwardIterator1 first1, ForwardIterator1 last1,
56             ForwardIterator2 first2, ForwardIterator2 last2);
57
58template <class ForwardIterator1, class ForwardIterator2, class BinaryPredicate>
59    ForwardIterator1            // constexpr in C++20
60    find_end(ForwardIterator1 first1, ForwardIterator1 last1,
61             ForwardIterator2 first2, ForwardIterator2 last2, BinaryPredicate pred);
62
63template <class ForwardIterator1, class ForwardIterator2>
64    constexpr ForwardIterator1  // constexpr in C++20
65    find_first_of(ForwardIterator1 first1, ForwardIterator1 last1,
66                  ForwardIterator2 first2, ForwardIterator2 last2);
67
68template <class ForwardIterator1, class ForwardIterator2, class BinaryPredicate>
69    constexpr ForwardIterator1  // constexpr in C++20
70    find_first_of(ForwardIterator1 first1, ForwardIterator1 last1,
71                  ForwardIterator2 first2, ForwardIterator2 last2, BinaryPredicate pred);
72
73template <class ForwardIterator>
74    constexpr ForwardIterator   // constexpr in C++20
75    adjacent_find(ForwardIterator first, ForwardIterator last);
76
77template <class ForwardIterator, class BinaryPredicate>
78    constexpr ForwardIterator   // constexpr in C++20
79    adjacent_find(ForwardIterator first, ForwardIterator last, BinaryPredicate pred);
80
81template <class InputIterator, class T>
82    constexpr typename iterator_traits<InputIterator>::difference_type  // constexpr in C++20
83    count(InputIterator first, InputIterator last, const T& value);
84
85template <class InputIterator, class Predicate>
86    constexpr typename iterator_traits<InputIterator>::difference_type // constexpr in C++20
87    count_if(InputIterator first, InputIterator last, Predicate pred);
88
89template <class InputIterator1, class InputIterator2>
90    constexpr pair<InputIterator1, InputIterator2>   // constexpr in C++20
91    mismatch(InputIterator1 first1, InputIterator1 last1, InputIterator2 first2);
92
93template <class InputIterator1, class InputIterator2>
94    constexpr pair<InputIterator1, InputIterator2>   // constexpr in C++20
95    mismatch(InputIterator1 first1, InputIterator1 last1,
96             InputIterator2 first2, InputIterator2 last2); // **C++14**
97
98template <class InputIterator1, class InputIterator2, class BinaryPredicate>
99    constexpr pair<InputIterator1, InputIterator2>   // constexpr in C++20
100    mismatch(InputIterator1 first1, InputIterator1 last1,
101             InputIterator2 first2, BinaryPredicate pred);
102
103template <class InputIterator1, class InputIterator2, class BinaryPredicate>
104    constexpr pair<InputIterator1, InputIterator2>   // constexpr in C++20
105    mismatch(InputIterator1 first1, InputIterator1 last1,
106             InputIterator2 first2, InputIterator2 last2,
107             BinaryPredicate pred); // **C++14**
108
109template <class InputIterator1, class InputIterator2>
110    constexpr bool      // constexpr in C++20
111    equal(InputIterator1 first1, InputIterator1 last1, InputIterator2 first2);
112
113template <class InputIterator1, class InputIterator2>
114    constexpr bool      // constexpr in C++20
115    equal(InputIterator1 first1, InputIterator1 last1,
116          InputIterator2 first2, InputIterator2 last2); // **C++14**
117
118template <class InputIterator1, class InputIterator2, class BinaryPredicate>
119    constexpr bool      // constexpr in C++20
120    equal(InputIterator1 first1, InputIterator1 last1,
121          InputIterator2 first2, BinaryPredicate pred);
122
123template <class InputIterator1, class InputIterator2, class BinaryPredicate>
124    constexpr bool      // constexpr in C++20
125    equal(InputIterator1 first1, InputIterator1 last1,
126          InputIterator2 first2, InputIterator2 last2,
127          BinaryPredicate pred); // **C++14**
128
129template<class ForwardIterator1, class ForwardIterator2>
130    constexpr bool      // constexpr in C++20
131    is_permutation(ForwardIterator1 first1, ForwardIterator1 last1,
132                   ForwardIterator2 first2);
133
134template<class ForwardIterator1, class ForwardIterator2>
135    constexpr bool      // constexpr in C++20
136    is_permutation(ForwardIterator1 first1, ForwardIterator1 last1,
137                   ForwardIterator2 first2, ForwardIterator2 last2); // **C++14**
138
139template<class ForwardIterator1, class ForwardIterator2, class BinaryPredicate>
140    constexpr bool      // constexpr in C++20
141    is_permutation(ForwardIterator1 first1, ForwardIterator1 last1,
142                   ForwardIterator2 first2, BinaryPredicate pred);
143
144template<class ForwardIterator1, class ForwardIterator2, class BinaryPredicate>
145    constexpr bool      // constexpr in C++20
146    is_permutation(ForwardIterator1 first1, ForwardIterator1 last1,
147                   ForwardIterator2 first2, ForwardIterator2 last2,
148                   BinaryPredicate pred);  // **C++14**
149
150template <class ForwardIterator1, class ForwardIterator2>
151    constexpr ForwardIterator1      // constexpr in C++20
152    search(ForwardIterator1 first1, ForwardIterator1 last1,
153           ForwardIterator2 first2, ForwardIterator2 last2);
154
155template <class ForwardIterator1, class ForwardIterator2, class BinaryPredicate>
156    constexpr ForwardIterator1      // constexpr in C++20
157    search(ForwardIterator1 first1, ForwardIterator1 last1,
158           ForwardIterator2 first2, ForwardIterator2 last2, BinaryPredicate pred);
159
160template <class ForwardIterator, class Size, class T>
161    constexpr ForwardIterator       // constexpr in C++20
162    search_n(ForwardIterator first, ForwardIterator last, Size count, const T& value);
163
164template <class ForwardIterator, class Size, class T, class BinaryPredicate>
165    constexpr ForwardIterator       // constexpr in C++20
166    search_n(ForwardIterator first, ForwardIterator last,
167             Size count, const T& value, BinaryPredicate pred);
168
169template <class InputIterator, class OutputIterator>
170    constexpr OutputIterator      // constexpr in C++20
171    copy(InputIterator first, InputIterator last, OutputIterator result);
172
173template<class InputIterator, class OutputIterator, class Predicate>
174    constexpr OutputIterator      // constexpr in C++20
175    copy_if(InputIterator first, InputIterator last,
176            OutputIterator result, Predicate pred);
177
178template<class InputIterator, class Size, class OutputIterator>
179    constexpr OutputIterator      // constexpr in C++20
180    copy_n(InputIterator first, Size n, OutputIterator result);
181
182template <class BidirectionalIterator1, class BidirectionalIterator2>
183    constexpr BidirectionalIterator2      // constexpr in C++20
184    copy_backward(BidirectionalIterator1 first, BidirectionalIterator1 last,
185                  BidirectionalIterator2 result);
186
187template <class ForwardIterator1, class ForwardIterator2>
188    ForwardIterator2
189    swap_ranges(ForwardIterator1 first1, ForwardIterator1 last1, ForwardIterator2 first2);
190
191template <class ForwardIterator1, class ForwardIterator2>
192    void
193    iter_swap(ForwardIterator1 a, ForwardIterator2 b);
194
195template <class InputIterator, class OutputIterator, class UnaryOperation>
196    constexpr OutputIterator      // constexpr in C++20
197    transform(InputIterator first, InputIterator last, OutputIterator result, UnaryOperation op);
198
199template <class InputIterator1, class InputIterator2, class OutputIterator, class BinaryOperation>
200    constexpr OutputIterator      // constexpr in C++20
201    transform(InputIterator1 first1, InputIterator1 last1, InputIterator2 first2,
202              OutputIterator result, BinaryOperation binary_op);
203
204template <class ForwardIterator, class T>
205    constexpr void      // constexpr in C++20
206    replace(ForwardIterator first, ForwardIterator last, const T& old_value, const T& new_value);
207
208template <class ForwardIterator, class Predicate, class T>
209    constexpr void      // constexpr in C++20
210    replace_if(ForwardIterator first, ForwardIterator last, Predicate pred, const T& new_value);
211
212template <class InputIterator, class OutputIterator, class T>
213    constexpr OutputIterator      // constexpr in C++20
214    replace_copy(InputIterator first, InputIterator last, OutputIterator result,
215                 const T& old_value, const T& new_value);
216
217template <class InputIterator, class OutputIterator, class Predicate, class T>
218    constexpr OutputIterator      // constexpr in C++20
219    replace_copy_if(InputIterator first, InputIterator last, OutputIterator result, Predicate pred, const T& new_value);
220
221template <class ForwardIterator, class T>
222    constexpr void      // constexpr in C++20
223    fill(ForwardIterator first, ForwardIterator last, const T& value);
224
225template <class OutputIterator, class Size, class T>
226    constexpr OutputIterator      // constexpr in C++20
227    fill_n(OutputIterator first, Size n, const T& value);
228
229template <class ForwardIterator, class Generator>
230    constexpr void      // constexpr in C++20
231    generate(ForwardIterator first, ForwardIterator last, Generator gen);
232
233template <class OutputIterator, class Size, class Generator>
234    constexpr OutputIterator      // constexpr in C++20
235    generate_n(OutputIterator first, Size n, Generator gen);
236
237template <class ForwardIterator, class T>
238    constexpr ForwardIterator     // constexpr in C++20
239    remove(ForwardIterator first, ForwardIterator last, const T& value);
240
241template <class ForwardIterator, class Predicate>
242    constexpr ForwardIterator     // constexpr in C++20
243    remove_if(ForwardIterator first, ForwardIterator last, Predicate pred);
244
245template <class InputIterator, class OutputIterator, class T>
246    constexpr OutputIterator     // constexpr in C++20
247    remove_copy(InputIterator first, InputIterator last, OutputIterator result, const T& value);
248
249template <class InputIterator, class OutputIterator, class Predicate>
250    constexpr OutputIterator     // constexpr in C++20
251    remove_copy_if(InputIterator first, InputIterator last, OutputIterator result, Predicate pred);
252
253template <class ForwardIterator>
254    ForwardIterator
255    unique(ForwardIterator first, ForwardIterator last);
256
257template <class ForwardIterator, class BinaryPredicate>
258    ForwardIterator
259    unique(ForwardIterator first, ForwardIterator last, BinaryPredicate pred);
260
261template <class InputIterator, class OutputIterator>
262    OutputIterator
263    unique_copy(InputIterator first, InputIterator last, OutputIterator result);
264
265template <class InputIterator, class OutputIterator, class BinaryPredicate>
266    OutputIterator
267    unique_copy(InputIterator first, InputIterator last, OutputIterator result, BinaryPredicate pred);
268
269template <class BidirectionalIterator>
270    void
271    reverse(BidirectionalIterator first, BidirectionalIterator last);
272
273template <class BidirectionalIterator, class OutputIterator>
274    constexpr OutputIterator       // constexpr in C++20
275    reverse_copy(BidirectionalIterator first, BidirectionalIterator last, OutputIterator result);
276
277template <class ForwardIterator>
278    ForwardIterator
279    rotate(ForwardIterator first, ForwardIterator middle, ForwardIterator last);
280
281template <class ForwardIterator, class OutputIterator>
282    OutputIterator
283    rotate_copy(ForwardIterator first, ForwardIterator middle, ForwardIterator last, OutputIterator result);
284
285template <class RandomAccessIterator>
286    void
287    random_shuffle(RandomAccessIterator first, RandomAccessIterator last); // deprecated in C++14, removed in C++17
288
289template <class RandomAccessIterator, class RandomNumberGenerator>
290    void
291    random_shuffle(RandomAccessIterator first, RandomAccessIterator last,
292                   RandomNumberGenerator& rand);  // deprecated in C++14, removed in C++17
293
294template<class PopulationIterator, class SampleIterator,
295         class Distance, class UniformRandomBitGenerator>
296    SampleIterator sample(PopulationIterator first, PopulationIterator last,
297                          SampleIterator out, Distance n,
298                          UniformRandomBitGenerator&& g); // C++17
299
300template<class RandomAccessIterator, class UniformRandomNumberGenerator>
301    void shuffle(RandomAccessIterator first, RandomAccessIterator last,
302                 UniformRandomNumberGenerator&& g);
303
304template <class InputIterator, class Predicate>
305    constexpr bool  // constexpr in C++20
306    is_partitioned(InputIterator first, InputIterator last, Predicate pred);
307
308template <class ForwardIterator, class Predicate>
309    ForwardIterator
310    partition(ForwardIterator first, ForwardIterator last, Predicate pred);
311
312template <class InputIterator, class OutputIterator1,
313          class OutputIterator2, class Predicate>
314    constexpr pair<OutputIterator1, OutputIterator2>   // constexpr in C++20
315    partition_copy(InputIterator first, InputIterator last,
316                   OutputIterator1 out_true, OutputIterator2 out_false,
317                   Predicate pred);
318
319template <class ForwardIterator, class Predicate>
320    ForwardIterator
321    stable_partition(ForwardIterator first, ForwardIterator last, Predicate pred);
322
323template<class ForwardIterator, class Predicate>
324    constexpr ForwardIterator  // constexpr in C++20
325    partition_point(ForwardIterator first, ForwardIterator last, Predicate pred);
326
327template <class ForwardIterator>
328    constexpr bool  // constexpr in C++20
329    is_sorted(ForwardIterator first, ForwardIterator last);
330
331template <class ForwardIterator, class Compare>
332    bool
333    is_sorted(ForwardIterator first, ForwardIterator last, Compare comp);
334
335template<class ForwardIterator>
336    constexpr ForwardIterator    // constexpr in C++20
337    is_sorted_until(ForwardIterator first, ForwardIterator last);
338
339template <class ForwardIterator, class Compare>
340    constexpr ForwardIterator    // constexpr in C++20
341    is_sorted_until(ForwardIterator first, ForwardIterator last, Compare comp);
342
343template <class RandomAccessIterator>
344    void
345    sort(RandomAccessIterator first, RandomAccessIterator last);
346
347template <class RandomAccessIterator, class Compare>
348    void
349    sort(RandomAccessIterator first, RandomAccessIterator last, Compare comp);
350
351template <class RandomAccessIterator>
352    void
353    stable_sort(RandomAccessIterator first, RandomAccessIterator last);
354
355template <class RandomAccessIterator, class Compare>
356    void
357    stable_sort(RandomAccessIterator first, RandomAccessIterator last, Compare comp);
358
359template <class RandomAccessIterator>
360    void
361    partial_sort(RandomAccessIterator first, RandomAccessIterator middle, RandomAccessIterator last);
362
363template <class RandomAccessIterator, class Compare>
364    void
365    partial_sort(RandomAccessIterator first, RandomAccessIterator middle, RandomAccessIterator last, Compare comp);
366
367template <class InputIterator, class RandomAccessIterator>
368    RandomAccessIterator
369    partial_sort_copy(InputIterator first, InputIterator last,
370                      RandomAccessIterator result_first, RandomAccessIterator result_last);
371
372template <class InputIterator, class RandomAccessIterator, class Compare>
373    RandomAccessIterator
374    partial_sort_copy(InputIterator first, InputIterator last,
375                      RandomAccessIterator result_first, RandomAccessIterator result_last, Compare comp);
376
377template <class RandomAccessIterator>
378    void
379    nth_element(RandomAccessIterator first, RandomAccessIterator nth, RandomAccessIterator last);
380
381template <class RandomAccessIterator, class Compare>
382    void
383    nth_element(RandomAccessIterator first, RandomAccessIterator nth, RandomAccessIterator last, Compare comp);
384
385template <class ForwardIterator, class T>
386    constexpr ForwardIterator                         // constexpr in C++20
387    lower_bound(ForwardIterator first, ForwardIterator last, const T& value);
388
389template <class ForwardIterator, class T, class Compare>
390    constexpr ForwardIterator                         // constexpr in C++20
391    lower_bound(ForwardIterator first, ForwardIterator last, const T& value, Compare comp);
392
393template <class ForwardIterator, class T>
394    constexpr ForwardIterator                         // constexpr in C++20
395    upper_bound(ForwardIterator first, ForwardIterator last, const T& value);
396
397template <class ForwardIterator, class T, class Compare>
398    constexpr ForwardIterator                         // constexpr in C++20
399    upper_bound(ForwardIterator first, ForwardIterator last, const T& value, Compare comp);
400
401template <class ForwardIterator, class T>
402    constexpr pair<ForwardIterator, ForwardIterator>  // constexpr in C++20
403    equal_range(ForwardIterator first, ForwardIterator last, const T& value);
404
405template <class ForwardIterator, class T, class Compare>
406    constexpr pair<ForwardIterator, ForwardIterator>  // constexpr in C++20
407    equal_range(ForwardIterator first, ForwardIterator last, const T& value, Compare comp);
408
409template <class ForwardIterator, class T>
410    constexpr bool                                    // constexpr in C++20
411    binary_search(ForwardIterator first, ForwardIterator last, const T& value);
412
413template <class ForwardIterator, class T, class Compare>
414    constexpr bool                                    // constexpr in C++20
415    binary_search(ForwardIterator first, ForwardIterator last, const T& value, Compare comp);
416
417template <class InputIterator1, class InputIterator2, class OutputIterator>
418    OutputIterator
419    merge(InputIterator1 first1, InputIterator1 last1,
420          InputIterator2 first2, InputIterator2 last2, OutputIterator result);
421
422template <class InputIterator1, class InputIterator2, class OutputIterator, class Compare>
423    OutputIterator
424    merge(InputIterator1 first1, InputIterator1 last1,
425          InputIterator2 first2, InputIterator2 last2, OutputIterator result, Compare comp);
426
427template <class BidirectionalIterator>
428    void
429    inplace_merge(BidirectionalIterator first, BidirectionalIterator middle, BidirectionalIterator last);
430
431template <class BidirectionalIterator, class Compare>
432    void
433    inplace_merge(BidirectionalIterator first, BidirectionalIterator middle, BidirectionalIterator last, Compare comp);
434
435template <class InputIterator1, class InputIterator2>
436    constexpr bool                                    // constexpr in C++20
437    includes(InputIterator1 first1, InputIterator1 last1, InputIterator2 first2, InputIterator2 last2);
438
439template <class InputIterator1, class InputIterator2, class Compare>
440    constexpr bool                                    // constexpr in C++20
441    includes(InputIterator1 first1, InputIterator1 last1, InputIterator2 first2, InputIterator2 last2, Compare comp);
442
443template <class InputIterator1, class InputIterator2, class OutputIterator>
444    OutputIterator
445    set_union(InputIterator1 first1, InputIterator1 last1,
446              InputIterator2 first2, InputIterator2 last2, OutputIterator result);
447
448template <class InputIterator1, class InputIterator2, class OutputIterator, class Compare>
449    OutputIterator
450    set_union(InputIterator1 first1, InputIterator1 last1,
451              InputIterator2 first2, InputIterator2 last2, OutputIterator result, Compare comp);
452
453template <class InputIterator1, class InputIterator2, class OutputIterator>
454    constexpr OutputIterator                         // constexpr in C++20
455    set_intersection(InputIterator1 first1, InputIterator1 last1,
456                     InputIterator2 first2, InputIterator2 last2, OutputIterator result);
457
458template <class InputIterator1, class InputIterator2, class OutputIterator, class Compare>
459    constexpr OutputIterator                         // constexpr in C++20
460    set_intersection(InputIterator1 first1, InputIterator1 last1,
461                     InputIterator2 first2, InputIterator2 last2, OutputIterator result, Compare comp);
462
463template <class InputIterator1, class InputIterator2, class OutputIterator>
464    OutputIterator
465    set_difference(InputIterator1 first1, InputIterator1 last1,
466                   InputIterator2 first2, InputIterator2 last2, OutputIterator result);
467
468template <class InputIterator1, class InputIterator2, class OutputIterator, class Compare>
469    OutputIterator
470    set_difference(InputIterator1 first1, InputIterator1 last1,
471                   InputIterator2 first2, InputIterator2 last2, OutputIterator result, Compare comp);
472
473template <class InputIterator1, class InputIterator2, class OutputIterator>
474    OutputIterator
475    set_symmetric_difference(InputIterator1 first1, InputIterator1 last1,
476                             InputIterator2 first2, InputIterator2 last2, OutputIterator result);
477
478template <class InputIterator1, class InputIterator2, class OutputIterator, class Compare>
479    OutputIterator
480    set_symmetric_difference(InputIterator1 first1, InputIterator1 last1,
481                             InputIterator2 first2, InputIterator2 last2, OutputIterator result, Compare comp);
482
483template <class RandomAccessIterator>
484    void
485    push_heap(RandomAccessIterator first, RandomAccessIterator last);
486
487template <class RandomAccessIterator, class Compare>
488    void
489    push_heap(RandomAccessIterator first, RandomAccessIterator last, Compare comp);
490
491template <class RandomAccessIterator>
492    void
493    pop_heap(RandomAccessIterator first, RandomAccessIterator last);
494
495template <class RandomAccessIterator, class Compare>
496    void
497    pop_heap(RandomAccessIterator first, RandomAccessIterator last, Compare comp);
498
499template <class RandomAccessIterator>
500    void
501    make_heap(RandomAccessIterator first, RandomAccessIterator last);
502
503template <class RandomAccessIterator, class Compare>
504    void
505    make_heap(RandomAccessIterator first, RandomAccessIterator last, Compare comp);
506
507template <class RandomAccessIterator>
508    void
509    sort_heap(RandomAccessIterator first, RandomAccessIterator last);
510
511template <class RandomAccessIterator, class Compare>
512    void
513    sort_heap(RandomAccessIterator first, RandomAccessIterator last, Compare comp);
514
515template <class RandomAccessIterator>
516    constexpr bool   // constexpr in C++20
517    is_heap(RandomAccessIterator first, RandomAccessiterator last);
518
519template <class RandomAccessIterator, class Compare>
520    constexpr bool   // constexpr in C++20
521    is_heap(RandomAccessIterator first, RandomAccessiterator last, Compare comp);
522
523template <class RandomAccessIterator>
524    constexpr RandomAccessIterator   // constexpr in C++20
525    is_heap_until(RandomAccessIterator first, RandomAccessiterator last);
526
527template <class RandomAccessIterator, class Compare>
528    constexpr RandomAccessIterator   // constexpr in C++20
529    is_heap_until(RandomAccessIterator first, RandomAccessiterator last, Compare comp);
530
531template <class ForwardIterator>
532    ForwardIterator
533    min_element(ForwardIterator first, ForwardIterator last);  // constexpr in C++14
534
535template <class ForwardIterator, class Compare>
536    ForwardIterator
537    min_element(ForwardIterator first, ForwardIterator last, Compare comp);  // constexpr in C++14
538
539template <class T>
540    const T&
541    min(const T& a, const T& b);  // constexpr in C++14
542
543template <class T, class Compare>
544    const T&
545    min(const T& a, const T& b, Compare comp);  // constexpr in C++14
546
547template<class T>
548    T
549    min(initializer_list<T> t);  // constexpr in C++14
550
551template<class T, class Compare>
552    T
553    min(initializer_list<T> t, Compare comp);  // constexpr in C++14
554
555template<class T>
556    constexpr const T& clamp( const T& v, const T& lo, const T& hi );               // C++17
557
558template<class T, class Compare>
559    constexpr const T& clamp( const T& v, const T& lo, const T& hi, Compare comp ); // C++17
560
561template <class ForwardIterator>
562    ForwardIterator
563    max_element(ForwardIterator first, ForwardIterator last);  // constexpr in C++14
564
565template <class ForwardIterator, class Compare>
566    ForwardIterator
567    max_element(ForwardIterator first, ForwardIterator last, Compare comp);  // constexpr in C++14
568
569template <class T>
570    const T&
571    max(const T& a, const T& b); // constexpr in C++14
572
573template <class T, class Compare>
574    const T&
575    max(const T& a, const T& b, Compare comp);  // constexpr in C++14
576
577template<class T>
578    T
579    max(initializer_list<T> t);  // constexpr in C++14
580
581template<class T, class Compare>
582    T
583    max(initializer_list<T> t, Compare comp);  // constexpr in C++14
584
585template<class ForwardIterator>
586    pair<ForwardIterator, ForwardIterator>
587    minmax_element(ForwardIterator first, ForwardIterator last);   // constexpr in C++14
588
589template<class ForwardIterator, class Compare>
590    pair<ForwardIterator, ForwardIterator>
591    minmax_element(ForwardIterator first, ForwardIterator last, Compare comp);   // constexpr in C++14
592
593template<class T>
594    pair<const T&, const T&>
595    minmax(const T& a, const T& b);  // constexpr in C++14
596
597template<class T, class Compare>
598    pair<const T&, const T&>
599    minmax(const T& a, const T& b, Compare comp);  // constexpr in C++14
600
601template<class T>
602    pair<T, T>
603    minmax(initializer_list<T> t);  // constexpr in C++14
604
605template<class T, class Compare>
606    pair<T, T>
607    minmax(initializer_list<T> t, Compare comp);  // constexpr in C++14
608
609template <class InputIterator1, class InputIterator2>
610    constexpr bool     // constexpr in C++20
611    lexicographical_compare(InputIterator1 first1, InputIterator1 last1, InputIterator2 first2, InputIterator2 last2);
612
613template <class InputIterator1, class InputIterator2, class Compare>
614    constexpr bool     // constexpr in C++20
615    lexicographical_compare(InputIterator1 first1, InputIterator1 last1,
616                            InputIterator2 first2, InputIterator2 last2, Compare comp);
617
618template <class BidirectionalIterator>
619    bool
620    next_permutation(BidirectionalIterator first, BidirectionalIterator last);
621
622template <class BidirectionalIterator, class Compare>
623    bool
624    next_permutation(BidirectionalIterator first, BidirectionalIterator last, Compare comp);
625
626template <class BidirectionalIterator>
627    bool
628    prev_permutation(BidirectionalIterator first, BidirectionalIterator last);
629
630template <class BidirectionalIterator, class Compare>
631    bool
632    prev_permutation(BidirectionalIterator first, BidirectionalIterator last, Compare comp);
633
634}  // std
635
636*/
637
638#include <__config>
639#include <initializer_list>
640#include <type_traits>
641#include <cstring>
642#include <utility> // needed to provide swap_ranges.
643#include <memory>
644#include <functional>
645#include <iterator>
646#include <cstddef>
647#include <bit>
648#include <version>
649
650#include <__debug>
651
652#if !defined(_LIBCPP_HAS_NO_PRAGMA_SYSTEM_HEADER)
653#pragma GCC system_header
654#endif
655
656_LIBCPP_PUSH_MACROS
657#include <__undef_macros>
658
659
660_LIBCPP_BEGIN_NAMESPACE_STD
661
662// I'd like to replace these with _VSTD::equal_to<void>, but can't because:
663//   * That only works with C++14 and later, and
664//   * We haven't included <functional> here.
665template <class _T1, class _T2 = _T1>
666struct __equal_to
667{
668    _LIBCPP_INLINE_VISIBILITY _LIBCPP_CONSTEXPR_AFTER_CXX11 bool operator()(const _T1& __x, const _T1& __y) const {return __x == __y;}
669    _LIBCPP_INLINE_VISIBILITY _LIBCPP_CONSTEXPR_AFTER_CXX11 bool operator()(const _T1& __x, const _T2& __y) const {return __x == __y;}
670    _LIBCPP_INLINE_VISIBILITY _LIBCPP_CONSTEXPR_AFTER_CXX11 bool operator()(const _T2& __x, const _T1& __y) const {return __x == __y;}
671    _LIBCPP_INLINE_VISIBILITY _LIBCPP_CONSTEXPR_AFTER_CXX11 bool operator()(const _T2& __x, const _T2& __y) const {return __x == __y;}
672};
673
674template <class _T1>
675struct __equal_to<_T1, _T1>
676{
677    _LIBCPP_INLINE_VISIBILITY _LIBCPP_CONSTEXPR_AFTER_CXX11
678    bool operator()(const _T1& __x, const _T1& __y) const {return __x == __y;}
679};
680
681template <class _T1>
682struct __equal_to<const _T1, _T1>
683{
684    _LIBCPP_INLINE_VISIBILITY _LIBCPP_CONSTEXPR_AFTER_CXX11
685    bool operator()(const _T1& __x, const _T1& __y) const {return __x == __y;}
686};
687
688template <class _T1>
689struct __equal_to<_T1, const _T1>
690{
691    _LIBCPP_INLINE_VISIBILITY _LIBCPP_CONSTEXPR_AFTER_CXX11
692    bool operator()(const _T1& __x, const _T1& __y) const {return __x == __y;}
693};
694
695template <class _T1, class _T2 = _T1>
696struct __less
697{
698    _LIBCPP_INLINE_VISIBILITY _LIBCPP_CONSTEXPR_AFTER_CXX11
699    bool operator()(const _T1& __x, const _T1& __y) const {return __x < __y;}
700
701    _LIBCPP_INLINE_VISIBILITY _LIBCPP_CONSTEXPR_AFTER_CXX11
702    bool operator()(const _T1& __x, const _T2& __y) const {return __x < __y;}
703
704    _LIBCPP_INLINE_VISIBILITY _LIBCPP_CONSTEXPR_AFTER_CXX11
705    bool operator()(const _T2& __x, const _T1& __y) const {return __x < __y;}
706
707    _LIBCPP_INLINE_VISIBILITY _LIBCPP_CONSTEXPR_AFTER_CXX11
708    bool operator()(const _T2& __x, const _T2& __y) const {return __x < __y;}
709};
710
711template <class _T1>
712struct __less<_T1, _T1>
713{
714    _LIBCPP_INLINE_VISIBILITY _LIBCPP_CONSTEXPR_AFTER_CXX11
715    bool operator()(const _T1& __x, const _T1& __y) const {return __x < __y;}
716};
717
718template <class _T1>
719struct __less<const _T1, _T1>
720{
721    _LIBCPP_INLINE_VISIBILITY _LIBCPP_CONSTEXPR_AFTER_CXX11
722    bool operator()(const _T1& __x, const _T1& __y) const {return __x < __y;}
723};
724
725template <class _T1>
726struct __less<_T1, const _T1>
727{
728    _LIBCPP_INLINE_VISIBILITY _LIBCPP_CONSTEXPR_AFTER_CXX11
729    bool operator()(const _T1& __x, const _T1& __y) const {return __x < __y;}
730};
731
732template <class _Predicate>
733class __invert // invert the sense of a comparison
734{
735private:
736    _Predicate __p_;
737public:
738    _LIBCPP_INLINE_VISIBILITY __invert() {}
739
740    _LIBCPP_INLINE_VISIBILITY
741    explicit __invert(_Predicate __p) : __p_(__p) {}
742
743    template <class _T1>
744    _LIBCPP_INLINE_VISIBILITY
745    bool operator()(const _T1& __x) {return !__p_(__x);}
746
747    template <class _T1, class _T2>
748    _LIBCPP_INLINE_VISIBILITY
749    bool operator()(const _T1& __x, const _T2& __y) {return __p_(__y, __x);}
750};
751
752// Perform division by two quickly for positive integers (llvm.org/PR39129)
753
754template <typename _Integral>
755_LIBCPP_INLINE_VISIBILITY _LIBCPP_CONSTEXPR
756typename enable_if
757<
758    is_integral<_Integral>::value,
759    _Integral
760>::type
761__half_positive(_Integral __value)
762{
763    return static_cast<_Integral>(static_cast<typename make_unsigned<_Integral>::type>(__value) / 2);
764}
765
766template <typename _Tp>
767_LIBCPP_INLINE_VISIBILITY _LIBCPP_CONSTEXPR
768typename enable_if
769<
770    !is_integral<_Tp>::value,
771    _Tp
772>::type
773__half_positive(_Tp __value)
774{
775    return __value / 2;
776}
777
778#ifdef _LIBCPP_DEBUG
779
780template <class _Compare>
781struct __debug_less
782{
783    _Compare &__comp_;
784    _LIBCPP_CONSTEXPR_AFTER_CXX17
785    __debug_less(_Compare& __c) : __comp_(__c) {}
786
787    template <class _Tp, class _Up>
788    _LIBCPP_CONSTEXPR_AFTER_CXX17
789    bool operator()(const _Tp& __x,  const _Up& __y)
790    {
791        bool __r = __comp_(__x, __y);
792        if (__r)
793            __do_compare_assert(0, __y, __x);
794        return __r;
795    }
796
797    template <class _Tp, class _Up>
798    _LIBCPP_CONSTEXPR_AFTER_CXX17
799    bool operator()(_Tp& __x,  _Up& __y)
800    {
801        bool __r = __comp_(__x, __y);
802        if (__r)
803            __do_compare_assert(0, __y, __x);
804        return __r;
805    }
806
807    template <class _LHS, class _RHS>
808    _LIBCPP_CONSTEXPR_AFTER_CXX17
809    inline _LIBCPP_INLINE_VISIBILITY
810    decltype((void)_VSTD::declval<_Compare&>()(
811        _VSTD::declval<_LHS &>(), _VSTD::declval<_RHS &>()))
812    __do_compare_assert(int, _LHS & __l, _RHS & __r) {
813        _LIBCPP_ASSERT(!__comp_(__l, __r),
814            "Comparator does not induce a strict weak ordering");
815    }
816
817    template <class _LHS, class _RHS>
818    _LIBCPP_CONSTEXPR_AFTER_CXX17
819    inline _LIBCPP_INLINE_VISIBILITY
820    void __do_compare_assert(long, _LHS &, _RHS &) {}
821};
822
823#endif // _LIBCPP_DEBUG
824
825template <class _Comp>
826struct __comp_ref_type {
827  // Pass the comparator by lvalue reference. Or in debug mode, using a
828  // debugging wrapper that stores a reference.
829#ifndef _LIBCPP_DEBUG
830  typedef typename add_lvalue_reference<_Comp>::type type;
831#else
832  typedef __debug_less<_Comp> type;
833#endif
834};
835
836// all_of
837
838template <class _InputIterator, class _Predicate>
839_LIBCPP_NODISCARD_EXT inline
840_LIBCPP_INLINE_VISIBILITY _LIBCPP_CONSTEXPR_AFTER_CXX17
841bool
842all_of(_InputIterator __first, _InputIterator __last, _Predicate __pred)
843{
844    for (; __first != __last; ++__first)
845        if (!__pred(*__first))
846            return false;
847    return true;
848}
849
850// any_of
851
852template <class _InputIterator, class _Predicate>
853_LIBCPP_NODISCARD_EXT inline
854_LIBCPP_INLINE_VISIBILITY _LIBCPP_CONSTEXPR_AFTER_CXX17
855bool
856any_of(_InputIterator __first, _InputIterator __last, _Predicate __pred)
857{
858    for (; __first != __last; ++__first)
859        if (__pred(*__first))
860            return true;
861    return false;
862}
863
864// none_of
865
866template <class _InputIterator, class _Predicate>
867_LIBCPP_NODISCARD_EXT inline
868_LIBCPP_INLINE_VISIBILITY _LIBCPP_CONSTEXPR_AFTER_CXX17
869bool
870none_of(_InputIterator __first, _InputIterator __last, _Predicate __pred)
871{
872    for (; __first != __last; ++__first)
873        if (__pred(*__first))
874            return false;
875    return true;
876}
877
878// for_each
879
880template <class _InputIterator, class _Function>
881inline _LIBCPP_INLINE_VISIBILITY _LIBCPP_CONSTEXPR_AFTER_CXX17
882_Function
883for_each(_InputIterator __first, _InputIterator __last, _Function __f)
884{
885    for (; __first != __last; ++__first)
886        __f(*__first);
887    return __f;
888}
889
890#if _LIBCPP_STD_VER > 14
891// for_each_n
892
893template <class _InputIterator, class _Size, class _Function>
894inline _LIBCPP_INLINE_VISIBILITY _LIBCPP_CONSTEXPR_AFTER_CXX17
895_InputIterator
896for_each_n(_InputIterator __first, _Size __orig_n, _Function __f)
897{
898    typedef decltype(__convert_to_integral(__orig_n)) _IntegralSize;
899    _IntegralSize __n = __orig_n;
900    while (__n > 0)
901    {
902         __f(*__first);
903         ++__first;
904         --__n;
905    }
906    return __first;
907}
908#endif
909
910// find
911
912template <class _InputIterator, class _Tp>
913_LIBCPP_NODISCARD_EXT inline
914_LIBCPP_INLINE_VISIBILITY _LIBCPP_CONSTEXPR_AFTER_CXX17
915_InputIterator
916find(_InputIterator __first, _InputIterator __last, const _Tp& __value_)
917{
918    for (; __first != __last; ++__first)
919        if (*__first == __value_)
920            break;
921    return __first;
922}
923
924// find_if
925
926template <class _InputIterator, class _Predicate>
927_LIBCPP_NODISCARD_EXT inline
928_LIBCPP_INLINE_VISIBILITY _LIBCPP_CONSTEXPR_AFTER_CXX17
929_InputIterator
930find_if(_InputIterator __first, _InputIterator __last, _Predicate __pred)
931{
932    for (; __first != __last; ++__first)
933        if (__pred(*__first))
934            break;
935    return __first;
936}
937
938// find_if_not
939
940template<class _InputIterator, class _Predicate>
941_LIBCPP_NODISCARD_EXT inline
942_LIBCPP_INLINE_VISIBILITY _LIBCPP_CONSTEXPR_AFTER_CXX17
943_InputIterator
944find_if_not(_InputIterator __first, _InputIterator __last, _Predicate __pred)
945{
946    for (; __first != __last; ++__first)
947        if (!__pred(*__first))
948            break;
949    return __first;
950}
951
952// find_end
953
954template <class _BinaryPredicate, class _ForwardIterator1, class _ForwardIterator2>
955_LIBCPP_CONSTEXPR_AFTER_CXX17 _ForwardIterator1
956__find_end(_ForwardIterator1 __first1, _ForwardIterator1 __last1,
957           _ForwardIterator2 __first2, _ForwardIterator2 __last2, _BinaryPredicate __pred,
958           forward_iterator_tag, forward_iterator_tag)
959{
960    // modeled after search algorithm
961    _ForwardIterator1 __r = __last1;  // __last1 is the "default" answer
962    if (__first2 == __last2)
963        return __r;
964    while (true)
965    {
966        while (true)
967        {
968            if (__first1 == __last1)         // if source exhausted return last correct answer
969                return __r;                  //    (or __last1 if never found)
970            if (__pred(*__first1, *__first2))
971                break;
972            ++__first1;
973        }
974        // *__first1 matches *__first2, now match elements after here
975        _ForwardIterator1 __m1 = __first1;
976        _ForwardIterator2 __m2 = __first2;
977        while (true)
978        {
979            if (++__m2 == __last2)
980            {                         // Pattern exhaused, record answer and search for another one
981                __r = __first1;
982                ++__first1;
983                break;
984            }
985            if (++__m1 == __last1)     // Source exhausted, return last answer
986                return __r;
987            if (!__pred(*__m1, *__m2))  // mismatch, restart with a new __first
988            {
989                ++__first1;
990                break;
991            }  // else there is a match, check next elements
992        }
993    }
994}
995
996template <class _BinaryPredicate, class _BidirectionalIterator1, class _BidirectionalIterator2>
997_LIBCPP_CONSTEXPR_AFTER_CXX17 _BidirectionalIterator1
998__find_end(_BidirectionalIterator1 __first1, _BidirectionalIterator1 __last1,
999           _BidirectionalIterator2 __first2, _BidirectionalIterator2 __last2, _BinaryPredicate __pred,
1000           bidirectional_iterator_tag, bidirectional_iterator_tag)
1001{
1002    // modeled after search algorithm (in reverse)
1003    if (__first2 == __last2)
1004        return __last1;  // Everything matches an empty sequence
1005    _BidirectionalIterator1 __l1 = __last1;
1006    _BidirectionalIterator2 __l2 = __last2;
1007    --__l2;
1008    while (true)
1009    {
1010        // Find last element in sequence 1 that matchs *(__last2-1), with a mininum of loop checks
1011        while (true)
1012        {
1013            if (__first1 == __l1)  // return __last1 if no element matches *__first2
1014                return __last1;
1015            if (__pred(*--__l1, *__l2))
1016                break;
1017        }
1018        // *__l1 matches *__l2, now match elements before here
1019        _BidirectionalIterator1 __m1 = __l1;
1020        _BidirectionalIterator2 __m2 = __l2;
1021        while (true)
1022        {
1023            if (__m2 == __first2)  // If pattern exhausted, __m1 is the answer (works for 1 element pattern)
1024                return __m1;
1025            if (__m1 == __first1)  // Otherwise if source exhaused, pattern not found
1026                return __last1;
1027            if (!__pred(*--__m1, *--__m2))  // if there is a mismatch, restart with a new __l1
1028            {
1029                break;
1030            }  // else there is a match, check next elements
1031        }
1032    }
1033}
1034
1035template <class _BinaryPredicate, class _RandomAccessIterator1, class _RandomAccessIterator2>
1036_LIBCPP_CONSTEXPR_AFTER_CXX11 _RandomAccessIterator1
1037__find_end(_RandomAccessIterator1 __first1, _RandomAccessIterator1 __last1,
1038           _RandomAccessIterator2 __first2, _RandomAccessIterator2 __last2, _BinaryPredicate __pred,
1039           random_access_iterator_tag, random_access_iterator_tag)
1040{
1041    // Take advantage of knowing source and pattern lengths.  Stop short when source is smaller than pattern
1042    typename iterator_traits<_RandomAccessIterator2>::difference_type __len2 = __last2 - __first2;
1043    if (__len2 == 0)
1044        return __last1;
1045    typename iterator_traits<_RandomAccessIterator1>::difference_type __len1 = __last1 - __first1;
1046    if (__len1 < __len2)
1047        return __last1;
1048    const _RandomAccessIterator1 __s = __first1 + (__len2 - 1);  // End of pattern match can't go before here
1049    _RandomAccessIterator1 __l1 = __last1;
1050    _RandomAccessIterator2 __l2 = __last2;
1051    --__l2;
1052    while (true)
1053    {
1054        while (true)
1055        {
1056            if (__s == __l1)
1057                return __last1;
1058            if (__pred(*--__l1, *__l2))
1059                break;
1060        }
1061        _RandomAccessIterator1 __m1 = __l1;
1062        _RandomAccessIterator2 __m2 = __l2;
1063        while (true)
1064        {
1065            if (__m2 == __first2)
1066                return __m1;
1067                                 // no need to check range on __m1 because __s guarantees we have enough source
1068            if (!__pred(*--__m1, *--__m2))
1069            {
1070                break;
1071            }
1072        }
1073    }
1074}
1075
1076template <class _ForwardIterator1, class _ForwardIterator2, class _BinaryPredicate>
1077_LIBCPP_NODISCARD_EXT inline
1078_LIBCPP_INLINE_VISIBILITY _LIBCPP_CONSTEXPR_AFTER_CXX17
1079_ForwardIterator1
1080find_end(_ForwardIterator1 __first1, _ForwardIterator1 __last1,
1081         _ForwardIterator2 __first2, _ForwardIterator2 __last2, _BinaryPredicate __pred)
1082{
1083    return _VSTD::__find_end<typename add_lvalue_reference<_BinaryPredicate>::type>
1084                         (__first1, __last1, __first2, __last2, __pred,
1085                          typename iterator_traits<_ForwardIterator1>::iterator_category(),
1086                          typename iterator_traits<_ForwardIterator2>::iterator_category());
1087}
1088
1089template <class _ForwardIterator1, class _ForwardIterator2>
1090_LIBCPP_NODISCARD_EXT inline
1091_LIBCPP_INLINE_VISIBILITY _LIBCPP_CONSTEXPR_AFTER_CXX17
1092_ForwardIterator1
1093find_end(_ForwardIterator1 __first1, _ForwardIterator1 __last1,
1094         _ForwardIterator2 __first2, _ForwardIterator2 __last2)
1095{
1096    typedef typename iterator_traits<_ForwardIterator1>::value_type __v1;
1097    typedef typename iterator_traits<_ForwardIterator2>::value_type __v2;
1098    return _VSTD::find_end(__first1, __last1, __first2, __last2, __equal_to<__v1, __v2>());
1099}
1100
1101// find_first_of
1102
1103template <class _ForwardIterator1, class _ForwardIterator2, class _BinaryPredicate>
1104_LIBCPP_CONSTEXPR_AFTER_CXX11 _ForwardIterator1
1105__find_first_of_ce(_ForwardIterator1 __first1, _ForwardIterator1 __last1,
1106              _ForwardIterator2 __first2, _ForwardIterator2 __last2, _BinaryPredicate __pred)
1107{
1108    for (; __first1 != __last1; ++__first1)
1109        for (_ForwardIterator2 __j = __first2; __j != __last2; ++__j)
1110            if (__pred(*__first1, *__j))
1111                return __first1;
1112    return __last1;
1113}
1114
1115
1116template <class _ForwardIterator1, class _ForwardIterator2, class _BinaryPredicate>
1117_LIBCPP_NODISCARD_EXT inline
1118_LIBCPP_INLINE_VISIBILITY _LIBCPP_CONSTEXPR_AFTER_CXX17
1119_ForwardIterator1
1120find_first_of(_ForwardIterator1 __first1, _ForwardIterator1 __last1,
1121              _ForwardIterator2 __first2, _ForwardIterator2 __last2, _BinaryPredicate __pred)
1122{
1123    return _VSTD::__find_first_of_ce(__first1, __last1, __first2, __last2, __pred);
1124}
1125
1126template <class _ForwardIterator1, class _ForwardIterator2>
1127_LIBCPP_NODISCARD_EXT inline
1128_LIBCPP_INLINE_VISIBILITY _LIBCPP_CONSTEXPR_AFTER_CXX17
1129_ForwardIterator1
1130find_first_of(_ForwardIterator1 __first1, _ForwardIterator1 __last1,
1131              _ForwardIterator2 __first2, _ForwardIterator2 __last2)
1132{
1133    typedef typename iterator_traits<_ForwardIterator1>::value_type __v1;
1134    typedef typename iterator_traits<_ForwardIterator2>::value_type __v2;
1135    return _VSTD::__find_first_of_ce(__first1, __last1, __first2, __last2, __equal_to<__v1, __v2>());
1136}
1137
1138// adjacent_find
1139
1140template <class _ForwardIterator, class _BinaryPredicate>
1141_LIBCPP_NODISCARD_EXT inline
1142_LIBCPP_INLINE_VISIBILITY _LIBCPP_CONSTEXPR_AFTER_CXX17
1143_ForwardIterator
1144adjacent_find(_ForwardIterator __first, _ForwardIterator __last, _BinaryPredicate __pred)
1145{
1146    if (__first != __last)
1147    {
1148        _ForwardIterator __i = __first;
1149        while (++__i != __last)
1150        {
1151            if (__pred(*__first, *__i))
1152                return __first;
1153            __first = __i;
1154        }
1155    }
1156    return __last;
1157}
1158
1159template <class _ForwardIterator>
1160_LIBCPP_NODISCARD_EXT inline
1161_LIBCPP_INLINE_VISIBILITY _LIBCPP_CONSTEXPR_AFTER_CXX17
1162_ForwardIterator
1163adjacent_find(_ForwardIterator __first, _ForwardIterator __last)
1164{
1165    typedef typename iterator_traits<_ForwardIterator>::value_type __v;
1166    return _VSTD::adjacent_find(__first, __last, __equal_to<__v>());
1167}
1168
1169// count
1170
1171template <class _InputIterator, class _Tp>
1172_LIBCPP_NODISCARD_EXT inline
1173_LIBCPP_INLINE_VISIBILITY _LIBCPP_CONSTEXPR_AFTER_CXX17
1174typename iterator_traits<_InputIterator>::difference_type
1175count(_InputIterator __first, _InputIterator __last, const _Tp& __value_)
1176{
1177    typename iterator_traits<_InputIterator>::difference_type __r(0);
1178    for (; __first != __last; ++__first)
1179        if (*__first == __value_)
1180            ++__r;
1181    return __r;
1182}
1183
1184// count_if
1185
1186template <class _InputIterator, class _Predicate>
1187_LIBCPP_NODISCARD_EXT inline
1188_LIBCPP_INLINE_VISIBILITY _LIBCPP_CONSTEXPR_AFTER_CXX17
1189typename iterator_traits<_InputIterator>::difference_type
1190count_if(_InputIterator __first, _InputIterator __last, _Predicate __pred)
1191{
1192    typename iterator_traits<_InputIterator>::difference_type __r(0);
1193    for (; __first != __last; ++__first)
1194        if (__pred(*__first))
1195            ++__r;
1196    return __r;
1197}
1198
1199// mismatch
1200
1201template <class _InputIterator1, class _InputIterator2, class _BinaryPredicate>
1202_LIBCPP_NODISCARD_EXT inline
1203_LIBCPP_INLINE_VISIBILITY _LIBCPP_CONSTEXPR_AFTER_CXX17
1204pair<_InputIterator1, _InputIterator2>
1205mismatch(_InputIterator1 __first1, _InputIterator1 __last1,
1206         _InputIterator2 __first2, _BinaryPredicate __pred)
1207{
1208    for (; __first1 != __last1; ++__first1, (void) ++__first2)
1209        if (!__pred(*__first1, *__first2))
1210            break;
1211    return pair<_InputIterator1, _InputIterator2>(__first1, __first2);
1212}
1213
1214template <class _InputIterator1, class _InputIterator2>
1215_LIBCPP_NODISCARD_EXT inline
1216_LIBCPP_INLINE_VISIBILITY _LIBCPP_CONSTEXPR_AFTER_CXX17
1217pair<_InputIterator1, _InputIterator2>
1218mismatch(_InputIterator1 __first1, _InputIterator1 __last1, _InputIterator2 __first2)
1219{
1220    typedef typename iterator_traits<_InputIterator1>::value_type __v1;
1221    typedef typename iterator_traits<_InputIterator2>::value_type __v2;
1222    return _VSTD::mismatch(__first1, __last1, __first2, __equal_to<__v1, __v2>());
1223}
1224
1225#if _LIBCPP_STD_VER > 11
1226template <class _InputIterator1, class _InputIterator2, class _BinaryPredicate>
1227_LIBCPP_NODISCARD_EXT inline
1228_LIBCPP_INLINE_VISIBILITY _LIBCPP_CONSTEXPR_AFTER_CXX17
1229pair<_InputIterator1, _InputIterator2>
1230mismatch(_InputIterator1 __first1, _InputIterator1 __last1,
1231         _InputIterator2 __first2, _InputIterator2 __last2,
1232         _BinaryPredicate __pred)
1233{
1234    for (; __first1 != __last1 && __first2 != __last2; ++__first1, (void) ++__first2)
1235        if (!__pred(*__first1, *__first2))
1236            break;
1237    return pair<_InputIterator1, _InputIterator2>(__first1, __first2);
1238}
1239
1240template <class _InputIterator1, class _InputIterator2>
1241_LIBCPP_NODISCARD_EXT inline
1242_LIBCPP_INLINE_VISIBILITY _LIBCPP_CONSTEXPR_AFTER_CXX17
1243pair<_InputIterator1, _InputIterator2>
1244mismatch(_InputIterator1 __first1, _InputIterator1 __last1,
1245         _InputIterator2 __first2, _InputIterator2 __last2)
1246{
1247    typedef typename iterator_traits<_InputIterator1>::value_type __v1;
1248    typedef typename iterator_traits<_InputIterator2>::value_type __v2;
1249    return _VSTD::mismatch(__first1, __last1, __first2, __last2, __equal_to<__v1, __v2>());
1250}
1251#endif
1252
1253// equal
1254
1255template <class _InputIterator1, class _InputIterator2, class _BinaryPredicate>
1256_LIBCPP_NODISCARD_EXT inline
1257_LIBCPP_INLINE_VISIBILITY _LIBCPP_CONSTEXPR_AFTER_CXX17
1258bool
1259equal(_InputIterator1 __first1, _InputIterator1 __last1, _InputIterator2 __first2, _BinaryPredicate __pred)
1260{
1261    for (; __first1 != __last1; ++__first1, (void) ++__first2)
1262        if (!__pred(*__first1, *__first2))
1263            return false;
1264    return true;
1265}
1266
1267template <class _InputIterator1, class _InputIterator2>
1268_LIBCPP_NODISCARD_EXT inline
1269_LIBCPP_INLINE_VISIBILITY _LIBCPP_CONSTEXPR_AFTER_CXX17
1270bool
1271equal(_InputIterator1 __first1, _InputIterator1 __last1, _InputIterator2 __first2)
1272{
1273    typedef typename iterator_traits<_InputIterator1>::value_type __v1;
1274    typedef typename iterator_traits<_InputIterator2>::value_type __v2;
1275    return _VSTD::equal(__first1, __last1, __first2, __equal_to<__v1, __v2>());
1276}
1277
1278#if _LIBCPP_STD_VER > 11
1279template <class _BinaryPredicate, class _InputIterator1, class _InputIterator2>
1280inline _LIBCPP_INLINE_VISIBILITY _LIBCPP_CONSTEXPR_AFTER_CXX17
1281bool
1282__equal(_InputIterator1 __first1, _InputIterator1 __last1,
1283        _InputIterator2 __first2, _InputIterator2 __last2, _BinaryPredicate __pred,
1284        input_iterator_tag, input_iterator_tag )
1285{
1286    for (; __first1 != __last1 && __first2 != __last2; ++__first1, (void) ++__first2)
1287        if (!__pred(*__first1, *__first2))
1288            return false;
1289    return __first1 == __last1 && __first2 == __last2;
1290}
1291
1292template <class _BinaryPredicate, class _RandomAccessIterator1, class _RandomAccessIterator2>
1293inline _LIBCPP_INLINE_VISIBILITY _LIBCPP_CONSTEXPR_AFTER_CXX17
1294bool
1295__equal(_RandomAccessIterator1 __first1, _RandomAccessIterator1 __last1,
1296        _RandomAccessIterator2 __first2, _RandomAccessIterator2 __last2, _BinaryPredicate __pred,
1297      random_access_iterator_tag, random_access_iterator_tag )
1298{
1299    if ( _VSTD::distance(__first1, __last1) != _VSTD::distance(__first2, __last2))
1300        return false;
1301    return _VSTD::equal<_RandomAccessIterator1, _RandomAccessIterator2,
1302                        typename add_lvalue_reference<_BinaryPredicate>::type>
1303                       (__first1, __last1, __first2, __pred );
1304}
1305
1306template <class _InputIterator1, class _InputIterator2, class _BinaryPredicate>
1307_LIBCPP_NODISCARD_EXT inline
1308_LIBCPP_INLINE_VISIBILITY _LIBCPP_CONSTEXPR_AFTER_CXX17
1309bool
1310equal(_InputIterator1 __first1, _InputIterator1 __last1,
1311      _InputIterator2 __first2, _InputIterator2 __last2, _BinaryPredicate __pred )
1312{
1313    return _VSTD::__equal<typename add_lvalue_reference<_BinaryPredicate>::type>
1314       (__first1, __last1, __first2, __last2, __pred,
1315        typename iterator_traits<_InputIterator1>::iterator_category(),
1316        typename iterator_traits<_InputIterator2>::iterator_category());
1317}
1318
1319template <class _InputIterator1, class _InputIterator2>
1320_LIBCPP_NODISCARD_EXT inline
1321_LIBCPP_INLINE_VISIBILITY _LIBCPP_CONSTEXPR_AFTER_CXX17
1322bool
1323equal(_InputIterator1 __first1, _InputIterator1 __last1,
1324      _InputIterator2 __first2, _InputIterator2 __last2)
1325{
1326    typedef typename iterator_traits<_InputIterator1>::value_type __v1;
1327    typedef typename iterator_traits<_InputIterator2>::value_type __v2;
1328    return _VSTD::__equal(__first1, __last1, __first2, __last2, __equal_to<__v1, __v2>(),
1329        typename iterator_traits<_InputIterator1>::iterator_category(),
1330        typename iterator_traits<_InputIterator2>::iterator_category());
1331}
1332#endif
1333
1334// is_permutation
1335
1336template<class _ForwardIterator1, class _ForwardIterator2, class _BinaryPredicate>
1337_LIBCPP_NODISCARD_EXT _LIBCPP_CONSTEXPR_AFTER_CXX17 bool
1338is_permutation(_ForwardIterator1 __first1, _ForwardIterator1 __last1,
1339               _ForwardIterator2 __first2, _BinaryPredicate __pred)
1340{
1341//  shorten sequences as much as possible by lopping of any equal prefix
1342    for (; __first1 != __last1; ++__first1, (void) ++__first2)
1343        if (!__pred(*__first1, *__first2))
1344            break;
1345    if (__first1 == __last1)
1346        return true;
1347
1348//  __first1 != __last1 && *__first1 != *__first2
1349    typedef typename iterator_traits<_ForwardIterator1>::difference_type _D1;
1350    _D1 __l1 = _VSTD::distance(__first1, __last1);
1351    if (__l1 == _D1(1))
1352        return false;
1353    _ForwardIterator2 __last2 = _VSTD::next(__first2, __l1);
1354    // For each element in [f1, l1) see if there are the same number of
1355    //    equal elements in [f2, l2)
1356    for (_ForwardIterator1 __i = __first1; __i != __last1; ++__i)
1357    {
1358    //  Have we already counted the number of *__i in [f1, l1)?
1359        _ForwardIterator1 __match = __first1;
1360        for (; __match != __i; ++__match)
1361            if (__pred(*__match, *__i))
1362                break;
1363        if (__match == __i) {
1364            // Count number of *__i in [f2, l2)
1365            _D1 __c2 = 0;
1366            for (_ForwardIterator2 __j = __first2; __j != __last2; ++__j)
1367                if (__pred(*__i, *__j))
1368                    ++__c2;
1369            if (__c2 == 0)
1370                return false;
1371            // Count number of *__i in [__i, l1) (we can start with 1)
1372            _D1 __c1 = 1;
1373            for (_ForwardIterator1 __j = _VSTD::next(__i); __j != __last1; ++__j)
1374                if (__pred(*__i, *__j))
1375                    ++__c1;
1376            if (__c1 != __c2)
1377                return false;
1378        }
1379    }
1380    return true;
1381}
1382
1383template<class _ForwardIterator1, class _ForwardIterator2>
1384_LIBCPP_NODISCARD_EXT inline
1385_LIBCPP_INLINE_VISIBILITY _LIBCPP_CONSTEXPR_AFTER_CXX17
1386bool
1387is_permutation(_ForwardIterator1 __first1, _ForwardIterator1 __last1,
1388               _ForwardIterator2 __first2)
1389{
1390    typedef typename iterator_traits<_ForwardIterator1>::value_type __v1;
1391    typedef typename iterator_traits<_ForwardIterator2>::value_type __v2;
1392    return _VSTD::is_permutation(__first1, __last1, __first2, __equal_to<__v1, __v2>());
1393}
1394
1395#if _LIBCPP_STD_VER > 11
1396template<class _BinaryPredicate, class _ForwardIterator1, class _ForwardIterator2>
1397_LIBCPP_CONSTEXPR_AFTER_CXX17 bool
1398__is_permutation(_ForwardIterator1 __first1, _ForwardIterator1 __last1,
1399                 _ForwardIterator2 __first2, _ForwardIterator2 __last2,
1400                 _BinaryPredicate __pred,
1401                 forward_iterator_tag, forward_iterator_tag )
1402{
1403//  shorten sequences as much as possible by lopping of any equal prefix
1404    for (; __first1 != __last1 && __first2 != __last2; ++__first1, (void) ++__first2)
1405        if (!__pred(*__first1, *__first2))
1406            break;
1407    if (__first1 == __last1)
1408        return __first2 == __last2;
1409    else if (__first2 == __last2)
1410        return false;
1411
1412    typedef typename iterator_traits<_ForwardIterator1>::difference_type _D1;
1413    _D1 __l1 = _VSTD::distance(__first1, __last1);
1414
1415    typedef typename iterator_traits<_ForwardIterator2>::difference_type _D2;
1416    _D2 __l2 = _VSTD::distance(__first2, __last2);
1417    if (__l1 != __l2)
1418        return false;
1419
1420    // For each element in [f1, l1) see if there are the same number of
1421    //    equal elements in [f2, l2)
1422    for (_ForwardIterator1 __i = __first1; __i != __last1; ++__i)
1423    {
1424    //  Have we already counted the number of *__i in [f1, l1)?
1425        _ForwardIterator1 __match = __first1;
1426        for (; __match != __i; ++__match)
1427            if (__pred(*__match, *__i))
1428                break;
1429        if (__match == __i) {
1430            // Count number of *__i in [f2, l2)
1431            _D1 __c2 = 0;
1432            for (_ForwardIterator2 __j = __first2; __j != __last2; ++__j)
1433                if (__pred(*__i, *__j))
1434                    ++__c2;
1435            if (__c2 == 0)
1436                return false;
1437            // Count number of *__i in [__i, l1) (we can start with 1)
1438            _D1 __c1 = 1;
1439            for (_ForwardIterator1 __j = _VSTD::next(__i); __j != __last1; ++__j)
1440                if (__pred(*__i, *__j))
1441                    ++__c1;
1442            if (__c1 != __c2)
1443                return false;
1444        }
1445    }
1446    return true;
1447}
1448
1449template<class _BinaryPredicate, class _RandomAccessIterator1, class _RandomAccessIterator2>
1450_LIBCPP_CONSTEXPR_AFTER_CXX17 bool
1451__is_permutation(_RandomAccessIterator1 __first1, _RandomAccessIterator2 __last1,
1452               _RandomAccessIterator1 __first2, _RandomAccessIterator2 __last2,
1453               _BinaryPredicate __pred,
1454               random_access_iterator_tag, random_access_iterator_tag )
1455{
1456    if ( _VSTD::distance(__first1, __last1) != _VSTD::distance(__first2, __last2))
1457        return false;
1458    return _VSTD::is_permutation<_RandomAccessIterator1, _RandomAccessIterator2,
1459                                 typename add_lvalue_reference<_BinaryPredicate>::type>
1460                                (__first1, __last1, __first2, __pred );
1461}
1462
1463template<class _ForwardIterator1, class _ForwardIterator2, class _BinaryPredicate>
1464_LIBCPP_NODISCARD_EXT inline
1465_LIBCPP_INLINE_VISIBILITY _LIBCPP_CONSTEXPR_AFTER_CXX17
1466bool
1467is_permutation(_ForwardIterator1 __first1, _ForwardIterator1 __last1,
1468               _ForwardIterator2 __first2, _ForwardIterator2 __last2,
1469               _BinaryPredicate __pred )
1470{
1471    return _VSTD::__is_permutation<typename add_lvalue_reference<_BinaryPredicate>::type>
1472       (__first1, __last1, __first2, __last2, __pred,
1473        typename iterator_traits<_ForwardIterator1>::iterator_category(),
1474        typename iterator_traits<_ForwardIterator2>::iterator_category());
1475}
1476
1477template<class _ForwardIterator1, class _ForwardIterator2>
1478_LIBCPP_NODISCARD_EXT inline
1479_LIBCPP_INLINE_VISIBILITY _LIBCPP_CONSTEXPR_AFTER_CXX17
1480bool
1481is_permutation(_ForwardIterator1 __first1, _ForwardIterator1 __last1,
1482               _ForwardIterator2 __first2, _ForwardIterator2 __last2)
1483{
1484    typedef typename iterator_traits<_ForwardIterator1>::value_type __v1;
1485    typedef typename iterator_traits<_ForwardIterator2>::value_type __v2;
1486    return _VSTD::__is_permutation(__first1, __last1, __first2, __last2,
1487        __equal_to<__v1, __v2>(),
1488        typename iterator_traits<_ForwardIterator1>::iterator_category(),
1489        typename iterator_traits<_ForwardIterator2>::iterator_category());
1490}
1491#endif
1492
1493// search
1494// __search is in <functional>
1495
1496template <class _ForwardIterator1, class _ForwardIterator2, class _BinaryPredicate>
1497_LIBCPP_NODISCARD_EXT inline
1498_LIBCPP_INLINE_VISIBILITY _LIBCPP_CONSTEXPR_AFTER_CXX17
1499_ForwardIterator1
1500search(_ForwardIterator1 __first1, _ForwardIterator1 __last1,
1501       _ForwardIterator2 __first2, _ForwardIterator2 __last2, _BinaryPredicate __pred)
1502{
1503    return _VSTD::__search<typename add_lvalue_reference<_BinaryPredicate>::type>
1504                         (__first1, __last1, __first2, __last2, __pred,
1505                          typename iterator_traits<_ForwardIterator1>::iterator_category(),
1506                          typename iterator_traits<_ForwardIterator2>::iterator_category())
1507            .first;
1508}
1509
1510template <class _ForwardIterator1, class _ForwardIterator2>
1511_LIBCPP_NODISCARD_EXT inline
1512_LIBCPP_INLINE_VISIBILITY _LIBCPP_CONSTEXPR_AFTER_CXX17
1513_ForwardIterator1
1514search(_ForwardIterator1 __first1, _ForwardIterator1 __last1,
1515       _ForwardIterator2 __first2, _ForwardIterator2 __last2)
1516{
1517    typedef typename iterator_traits<_ForwardIterator1>::value_type __v1;
1518    typedef typename iterator_traits<_ForwardIterator2>::value_type __v2;
1519    return _VSTD::search(__first1, __last1, __first2, __last2, __equal_to<__v1, __v2>());
1520}
1521
1522
1523#if _LIBCPP_STD_VER > 14
1524template <class _ForwardIterator, class _Searcher>
1525_LIBCPP_NODISCARD_EXT _LIBCPP_INLINE_VISIBILITY _LIBCPP_CONSTEXPR_AFTER_CXX17
1526_ForwardIterator search(_ForwardIterator __f, _ForwardIterator __l, const _Searcher &__s)
1527{ return __s(__f, __l).first; }
1528#endif
1529
1530// search_n
1531
1532template <class _BinaryPredicate, class _ForwardIterator, class _Size, class _Tp>
1533_LIBCPP_CONSTEXPR_AFTER_CXX17 _ForwardIterator
1534__search_n(_ForwardIterator __first, _ForwardIterator __last,
1535           _Size __count, const _Tp& __value_, _BinaryPredicate __pred, forward_iterator_tag)
1536{
1537    if (__count <= 0)
1538        return __first;
1539    while (true)
1540    {
1541        // Find first element in sequence that matchs __value_, with a mininum of loop checks
1542        while (true)
1543        {
1544            if (__first == __last)  // return __last if no element matches __value_
1545                return __last;
1546            if (__pred(*__first, __value_))
1547                break;
1548            ++__first;
1549        }
1550        // *__first matches __value_, now match elements after here
1551        _ForwardIterator __m = __first;
1552        _Size __c(0);
1553        while (true)
1554        {
1555            if (++__c == __count)  // If pattern exhausted, __first is the answer (works for 1 element pattern)
1556                return __first;
1557            if (++__m == __last)  // Otherwise if source exhaused, pattern not found
1558                return __last;
1559            if (!__pred(*__m, __value_))  // if there is a mismatch, restart with a new __first
1560            {
1561                __first = __m;
1562                ++__first;
1563                break;
1564            }  // else there is a match, check next elements
1565        }
1566    }
1567}
1568
1569template <class _BinaryPredicate, class _RandomAccessIterator, class _Size, class _Tp>
1570_LIBCPP_CONSTEXPR_AFTER_CXX17 _RandomAccessIterator
1571__search_n(_RandomAccessIterator __first, _RandomAccessIterator __last,
1572           _Size __count, const _Tp& __value_, _BinaryPredicate __pred, random_access_iterator_tag)
1573{
1574    if (__count <= 0)
1575        return __first;
1576    _Size __len = static_cast<_Size>(__last - __first);
1577    if (__len < __count)
1578        return __last;
1579    const _RandomAccessIterator __s = __last - (__count - 1);  // Start of pattern match can't go beyond here
1580    while (true)
1581    {
1582        // Find first element in sequence that matchs __value_, with a mininum of loop checks
1583        while (true)
1584        {
1585            if (__first >= __s)  // return __last if no element matches __value_
1586                return __last;
1587            if (__pred(*__first, __value_))
1588                break;
1589            ++__first;
1590        }
1591        // *__first matches __value_, now match elements after here
1592        _RandomAccessIterator __m = __first;
1593        _Size __c(0);
1594        while (true)
1595        {
1596            if (++__c == __count)  // If pattern exhausted, __first is the answer (works for 1 element pattern)
1597                return __first;
1598             ++__m;          // no need to check range on __m because __s guarantees we have enough source
1599            if (!__pred(*__m, __value_))  // if there is a mismatch, restart with a new __first
1600            {
1601                __first = __m;
1602                ++__first;
1603                break;
1604            }  // else there is a match, check next elements
1605        }
1606    }
1607}
1608
1609template <class _ForwardIterator, class _Size, class _Tp, class _BinaryPredicate>
1610_LIBCPP_NODISCARD_EXT inline
1611_LIBCPP_INLINE_VISIBILITY _LIBCPP_CONSTEXPR_AFTER_CXX17
1612_ForwardIterator
1613search_n(_ForwardIterator __first, _ForwardIterator __last,
1614         _Size __count, const _Tp& __value_, _BinaryPredicate __pred)
1615{
1616    return _VSTD::__search_n<typename add_lvalue_reference<_BinaryPredicate>::type>
1617           (__first, __last, __convert_to_integral(__count), __value_, __pred,
1618           typename iterator_traits<_ForwardIterator>::iterator_category());
1619}
1620
1621template <class _ForwardIterator, class _Size, class _Tp>
1622_LIBCPP_NODISCARD_EXT inline
1623_LIBCPP_INLINE_VISIBILITY _LIBCPP_CONSTEXPR_AFTER_CXX17
1624_ForwardIterator
1625search_n(_ForwardIterator __first, _ForwardIterator __last, _Size __count, const _Tp& __value_)
1626{
1627    typedef typename iterator_traits<_ForwardIterator>::value_type __v;
1628    return _VSTD::search_n(__first, __last, __convert_to_integral(__count),
1629                           __value_, __equal_to<__v, _Tp>());
1630}
1631
1632// copy
1633template <class _Iter>
1634inline _LIBCPP_INLINE_VISIBILITY _LIBCPP_CONSTEXPR_AFTER_CXX17
1635_Iter
1636__unwrap_iter(_Iter __i)
1637{
1638    return __i;
1639}
1640
1641template <class _Tp>
1642inline _LIBCPP_INLINE_VISIBILITY _LIBCPP_CONSTEXPR_AFTER_CXX17
1643typename enable_if
1644<
1645    is_trivially_copy_assignable<_Tp>::value,
1646    _Tp*
1647>::type
1648__unwrap_iter(move_iterator<_Tp*> __i)
1649{
1650    return __i.base();
1651}
1652
1653#if _LIBCPP_DEBUG_LEVEL < 2
1654
1655template <class _Tp>
1656inline _LIBCPP_INLINE_VISIBILITY _LIBCPP_CONSTEXPR_IF_NODEBUG
1657typename enable_if
1658<
1659    is_trivially_copy_assignable<_Tp>::value,
1660    _Tp*
1661>::type
1662__unwrap_iter(__wrap_iter<_Tp*> __i)
1663{
1664    return __i.base();
1665}
1666
1667template <class _Tp>
1668inline _LIBCPP_INLINE_VISIBILITY _LIBCPP_CONSTEXPR_IF_NODEBUG
1669typename enable_if
1670<
1671    is_trivially_copy_assignable<_Tp>::value,
1672    const _Tp*
1673>::type
1674__unwrap_iter(__wrap_iter<const _Tp*> __i)
1675{
1676    return __i.base();
1677}
1678
1679#else
1680
1681template <class _Tp>
1682inline _LIBCPP_INLINE_VISIBILITY _LIBCPP_CONSTEXPR_IF_NODEBUG
1683typename enable_if
1684<
1685    is_trivially_copy_assignable<_Tp>::value,
1686    __wrap_iter<_Tp*>
1687>::type
1688__unwrap_iter(__wrap_iter<_Tp*> __i)
1689{
1690    return __i;
1691}
1692
1693#endif  // _LIBCPP_DEBUG_LEVEL < 2
1694
1695template <class _InputIterator, class _OutputIterator>
1696inline _LIBCPP_INLINE_VISIBILITY _LIBCPP_CONSTEXPR_AFTER_CXX17
1697_OutputIterator
1698__copy_constexpr(_InputIterator __first, _InputIterator __last, _OutputIterator __result)
1699{
1700    for (; __first != __last; ++__first, (void) ++__result)
1701        *__result = *__first;
1702    return __result;
1703}
1704
1705template <class _InputIterator, class _OutputIterator>
1706inline _LIBCPP_INLINE_VISIBILITY
1707_OutputIterator
1708__copy(_InputIterator __first, _InputIterator __last, _OutputIterator __result)
1709{
1710    return __copy_constexpr(__first, __last, __result);
1711}
1712
1713template <class _Tp, class _Up>
1714inline _LIBCPP_INLINE_VISIBILITY
1715typename enable_if
1716<
1717    is_same<typename remove_const<_Tp>::type, _Up>::value &&
1718    is_trivially_copy_assignable<_Up>::value,
1719    _Up*
1720>::type
1721__copy(_Tp* __first, _Tp* __last, _Up* __result)
1722{
1723    const size_t __n = static_cast<size_t>(__last - __first);
1724    if (__n > 0)
1725        _VSTD::memmove(__result, __first, __n * sizeof(_Up));
1726    return __result + __n;
1727}
1728
1729template <class _InputIterator, class _OutputIterator>
1730inline _LIBCPP_INLINE_VISIBILITY _LIBCPP_CONSTEXPR_AFTER_CXX17_WITH_IS_CONSTANT_EVALUATED
1731_OutputIterator
1732copy(_InputIterator __first, _InputIterator __last, _OutputIterator __result)
1733{
1734    if (__libcpp_is_constant_evaluated()) {
1735        return _VSTD::__copy_constexpr(
1736            __unwrap_iter(__first), __unwrap_iter(__last), __unwrap_iter(__result));
1737    } else {
1738        return _VSTD::__copy(
1739            __unwrap_iter(__first), __unwrap_iter(__last), __unwrap_iter(__result));
1740    }
1741}
1742
1743// copy_backward
1744
1745template <class _BidirectionalIterator, class _OutputIterator>
1746inline _LIBCPP_INLINE_VISIBILITY _LIBCPP_CONSTEXPR_AFTER_CXX17
1747_OutputIterator
1748__copy_backward_constexpr(_BidirectionalIterator __first, _BidirectionalIterator __last, _OutputIterator __result)
1749{
1750    while (__first != __last)
1751        *--__result = *--__last;
1752    return __result;
1753}
1754
1755template <class _BidirectionalIterator, class _OutputIterator>
1756inline _LIBCPP_INLINE_VISIBILITY
1757_OutputIterator
1758__copy_backward(_BidirectionalIterator __first, _BidirectionalIterator __last, _OutputIterator __result)
1759{
1760    return __copy_backward_constexpr(__first, __last, __result);
1761}
1762
1763template <class _Tp, class _Up>
1764inline _LIBCPP_INLINE_VISIBILITY
1765typename enable_if
1766<
1767    is_same<typename remove_const<_Tp>::type, _Up>::value &&
1768    is_trivially_copy_assignable<_Up>::value,
1769    _Up*
1770>::type
1771__copy_backward(_Tp* __first, _Tp* __last, _Up* __result)
1772{
1773    const size_t __n = static_cast<size_t>(__last - __first);
1774    if (__n > 0)
1775    {
1776        __result -= __n;
1777        _VSTD::memmove(__result, __first, __n * sizeof(_Up));
1778    }
1779    return __result;
1780}
1781
1782template <class _BidirectionalIterator1, class _BidirectionalIterator2>
1783inline _LIBCPP_INLINE_VISIBILITY _LIBCPP_CONSTEXPR_AFTER_CXX17_WITH_IS_CONSTANT_EVALUATED
1784_BidirectionalIterator2
1785copy_backward(_BidirectionalIterator1 __first, _BidirectionalIterator1 __last,
1786              _BidirectionalIterator2 __result)
1787{
1788    if (__libcpp_is_constant_evaluated()) {
1789        return _VSTD::__copy_backward_constexpr(__unwrap_iter(__first),
1790                                                __unwrap_iter(__last),
1791                                                __unwrap_iter(__result));
1792    } else {
1793        return _VSTD::__copy_backward(__unwrap_iter(__first),
1794                                      __unwrap_iter(__last),
1795                                      __unwrap_iter(__result));
1796    }
1797}
1798
1799// copy_if
1800
1801template<class _InputIterator, class _OutputIterator, class _Predicate>
1802inline _LIBCPP_INLINE_VISIBILITY _LIBCPP_CONSTEXPR_AFTER_CXX17
1803_OutputIterator
1804copy_if(_InputIterator __first, _InputIterator __last,
1805        _OutputIterator __result, _Predicate __pred)
1806{
1807    for (; __first != __last; ++__first)
1808    {
1809        if (__pred(*__first))
1810        {
1811            *__result = *__first;
1812            ++__result;
1813        }
1814    }
1815    return __result;
1816}
1817
1818// copy_n
1819
1820template<class _InputIterator, class _Size, class _OutputIterator>
1821inline _LIBCPP_INLINE_VISIBILITY _LIBCPP_CONSTEXPR_AFTER_CXX17_WITH_IS_CONSTANT_EVALUATED
1822typename enable_if
1823<
1824    __is_cpp17_input_iterator<_InputIterator>::value &&
1825   !__is_cpp17_random_access_iterator<_InputIterator>::value,
1826    _OutputIterator
1827>::type
1828copy_n(_InputIterator __first, _Size __orig_n, _OutputIterator __result)
1829{
1830    typedef decltype(__convert_to_integral(__orig_n)) _IntegralSize;
1831    _IntegralSize __n = __orig_n;
1832    if (__n > 0)
1833    {
1834        *__result = *__first;
1835        ++__result;
1836        for (--__n; __n > 0; --__n)
1837        {
1838            ++__first;
1839            *__result = *__first;
1840            ++__result;
1841        }
1842    }
1843    return __result;
1844}
1845
1846template<class _InputIterator, class _Size, class _OutputIterator>
1847inline _LIBCPP_INLINE_VISIBILITY _LIBCPP_CONSTEXPR_AFTER_CXX17_WITH_IS_CONSTANT_EVALUATED
1848typename enable_if
1849<
1850    __is_cpp17_random_access_iterator<_InputIterator>::value,
1851    _OutputIterator
1852>::type
1853copy_n(_InputIterator __first, _Size __orig_n, _OutputIterator __result)
1854{
1855    typedef decltype(__convert_to_integral(__orig_n)) _IntegralSize;
1856    _IntegralSize __n = __orig_n;
1857    return _VSTD::copy(__first, __first + __n, __result);
1858}
1859
1860// move
1861
1862template <class _InputIterator, class _OutputIterator>
1863inline _LIBCPP_INLINE_VISIBILITY
1864_OutputIterator
1865__move(_InputIterator __first, _InputIterator __last, _OutputIterator __result)
1866{
1867    for (; __first != __last; ++__first, (void) ++__result)
1868        *__result = _VSTD::move(*__first);
1869    return __result;
1870}
1871
1872template <class _Tp, class _Up>
1873inline _LIBCPP_INLINE_VISIBILITY
1874typename enable_if
1875<
1876    is_same<typename remove_const<_Tp>::type, _Up>::value &&
1877    is_trivially_copy_assignable<_Up>::value,
1878    _Up*
1879>::type
1880__move(_Tp* __first, _Tp* __last, _Up* __result)
1881{
1882    const size_t __n = static_cast<size_t>(__last - __first);
1883    if (__n > 0)
1884        _VSTD::memmove(__result, __first, __n * sizeof(_Up));
1885    return __result + __n;
1886}
1887
1888template <class _InputIterator, class _OutputIterator>
1889inline _LIBCPP_INLINE_VISIBILITY
1890_OutputIterator
1891move(_InputIterator __first, _InputIterator __last, _OutputIterator __result)
1892{
1893    return _VSTD::__move(__unwrap_iter(__first), __unwrap_iter(__last), __unwrap_iter(__result));
1894}
1895
1896// move_backward
1897
1898template <class _InputIterator, class _OutputIterator>
1899inline _LIBCPP_INLINE_VISIBILITY
1900_OutputIterator
1901__move_backward(_InputIterator __first, _InputIterator __last, _OutputIterator __result)
1902{
1903    while (__first != __last)
1904        *--__result = _VSTD::move(*--__last);
1905    return __result;
1906}
1907
1908template <class _Tp, class _Up>
1909inline _LIBCPP_INLINE_VISIBILITY
1910typename enable_if
1911<
1912    is_same<typename remove_const<_Tp>::type, _Up>::value &&
1913    is_trivially_copy_assignable<_Up>::value,
1914    _Up*
1915>::type
1916__move_backward(_Tp* __first, _Tp* __last, _Up* __result)
1917{
1918    const size_t __n = static_cast<size_t>(__last - __first);
1919    if (__n > 0)
1920    {
1921        __result -= __n;
1922        _VSTD::memmove(__result, __first, __n * sizeof(_Up));
1923    }
1924    return __result;
1925}
1926
1927template <class _BidirectionalIterator1, class _BidirectionalIterator2>
1928inline _LIBCPP_INLINE_VISIBILITY
1929_BidirectionalIterator2
1930move_backward(_BidirectionalIterator1 __first, _BidirectionalIterator1 __last,
1931              _BidirectionalIterator2 __result)
1932{
1933    return _VSTD::__move_backward(__unwrap_iter(__first), __unwrap_iter(__last), __unwrap_iter(__result));
1934}
1935
1936// iter_swap
1937
1938// moved to <type_traits> for better swap / noexcept support
1939
1940// transform
1941
1942template <class _InputIterator, class _OutputIterator, class _UnaryOperation>
1943inline _LIBCPP_INLINE_VISIBILITY _LIBCPP_CONSTEXPR_AFTER_CXX17
1944_OutputIterator
1945transform(_InputIterator __first, _InputIterator __last, _OutputIterator __result, _UnaryOperation __op)
1946{
1947    for (; __first != __last; ++__first, (void) ++__result)
1948        *__result = __op(*__first);
1949    return __result;
1950}
1951
1952template <class _InputIterator1, class _InputIterator2, class _OutputIterator, class _BinaryOperation>
1953inline _LIBCPP_INLINE_VISIBILITY _LIBCPP_CONSTEXPR_AFTER_CXX17
1954_OutputIterator
1955transform(_InputIterator1 __first1, _InputIterator1 __last1, _InputIterator2 __first2,
1956          _OutputIterator __result, _BinaryOperation __binary_op)
1957{
1958    for (; __first1 != __last1; ++__first1, (void) ++__first2, ++__result)
1959        *__result = __binary_op(*__first1, *__first2);
1960    return __result;
1961}
1962
1963// replace
1964
1965template <class _ForwardIterator, class _Tp>
1966inline _LIBCPP_INLINE_VISIBILITY _LIBCPP_CONSTEXPR_AFTER_CXX17
1967void
1968replace(_ForwardIterator __first, _ForwardIterator __last, const _Tp& __old_value, const _Tp& __new_value)
1969{
1970    for (; __first != __last; ++__first)
1971        if (*__first == __old_value)
1972            *__first = __new_value;
1973}
1974
1975// replace_if
1976
1977template <class _ForwardIterator, class _Predicate, class _Tp>
1978inline _LIBCPP_INLINE_VISIBILITY _LIBCPP_CONSTEXPR_AFTER_CXX17
1979void
1980replace_if(_ForwardIterator __first, _ForwardIterator __last, _Predicate __pred, const _Tp& __new_value)
1981{
1982    for (; __first != __last; ++__first)
1983        if (__pred(*__first))
1984            *__first = __new_value;
1985}
1986
1987// replace_copy
1988
1989template <class _InputIterator, class _OutputIterator, class _Tp>
1990inline _LIBCPP_INLINE_VISIBILITY _LIBCPP_CONSTEXPR_AFTER_CXX17
1991_OutputIterator
1992replace_copy(_InputIterator __first, _InputIterator __last, _OutputIterator __result,
1993             const _Tp& __old_value, const _Tp& __new_value)
1994{
1995    for (; __first != __last; ++__first, (void) ++__result)
1996        if (*__first == __old_value)
1997            *__result = __new_value;
1998        else
1999            *__result = *__first;
2000    return __result;
2001}
2002
2003// replace_copy_if
2004
2005template <class _InputIterator, class _OutputIterator, class _Predicate, class _Tp>
2006inline _LIBCPP_INLINE_VISIBILITY _LIBCPP_CONSTEXPR_AFTER_CXX17
2007_OutputIterator
2008replace_copy_if(_InputIterator __first, _InputIterator __last, _OutputIterator __result,
2009                _Predicate __pred, const _Tp& __new_value)
2010{
2011    for (; __first != __last; ++__first, (void) ++__result)
2012        if (__pred(*__first))
2013            *__result = __new_value;
2014        else
2015            *__result = *__first;
2016    return __result;
2017}
2018
2019// fill_n
2020
2021template <class _OutputIterator, class _Size, class _Tp>
2022inline _LIBCPP_INLINE_VISIBILITY _LIBCPP_CONSTEXPR_AFTER_CXX17
2023_OutputIterator
2024__fill_n(_OutputIterator __first, _Size __n, const _Tp& __value_)
2025{
2026    for (; __n > 0; ++__first, (void) --__n)
2027        *__first = __value_;
2028    return __first;
2029}
2030
2031template <class _OutputIterator, class _Size, class _Tp>
2032inline _LIBCPP_INLINE_VISIBILITY _LIBCPP_CONSTEXPR_AFTER_CXX17
2033_OutputIterator
2034fill_n(_OutputIterator __first, _Size __n, const _Tp& __value_)
2035{
2036   return _VSTD::__fill_n(__first, __convert_to_integral(__n), __value_);
2037}
2038
2039// fill
2040
2041template <class _ForwardIterator, class _Tp>
2042inline _LIBCPP_INLINE_VISIBILITY _LIBCPP_CONSTEXPR_AFTER_CXX17
2043void
2044__fill(_ForwardIterator __first, _ForwardIterator __last, const _Tp& __value_, forward_iterator_tag)
2045{
2046    for (; __first != __last; ++__first)
2047        *__first = __value_;
2048}
2049
2050template <class _RandomAccessIterator, class _Tp>
2051inline _LIBCPP_INLINE_VISIBILITY _LIBCPP_CONSTEXPR_AFTER_CXX17
2052void
2053__fill(_RandomAccessIterator __first, _RandomAccessIterator __last, const _Tp& __value_, random_access_iterator_tag)
2054{
2055    _VSTD::fill_n(__first, __last - __first, __value_);
2056}
2057
2058template <class _ForwardIterator, class _Tp>
2059inline _LIBCPP_INLINE_VISIBILITY _LIBCPP_CONSTEXPR_AFTER_CXX17
2060void
2061fill(_ForwardIterator __first, _ForwardIterator __last, const _Tp& __value_)
2062{
2063    _VSTD::__fill(__first, __last, __value_, typename iterator_traits<_ForwardIterator>::iterator_category());
2064}
2065
2066// generate
2067
2068template <class _ForwardIterator, class _Generator>
2069inline _LIBCPP_INLINE_VISIBILITY _LIBCPP_CONSTEXPR_AFTER_CXX17
2070void
2071generate(_ForwardIterator __first, _ForwardIterator __last, _Generator __gen)
2072{
2073    for (; __first != __last; ++__first)
2074        *__first = __gen();
2075}
2076
2077// generate_n
2078
2079template <class _OutputIterator, class _Size, class _Generator>
2080inline _LIBCPP_INLINE_VISIBILITY _LIBCPP_CONSTEXPR_AFTER_CXX17
2081_OutputIterator
2082generate_n(_OutputIterator __first, _Size __orig_n, _Generator __gen)
2083{
2084    typedef decltype(__convert_to_integral(__orig_n)) _IntegralSize;
2085    _IntegralSize __n = __orig_n;
2086    for (; __n > 0; ++__first, (void) --__n)
2087        *__first = __gen();
2088    return __first;
2089}
2090
2091// remove
2092
2093template <class _ForwardIterator, class _Tp>
2094_LIBCPP_NODISCARD_EXT _LIBCPP_CONSTEXPR_AFTER_CXX17 _ForwardIterator
2095remove(_ForwardIterator __first, _ForwardIterator __last, const _Tp& __value_)
2096{
2097    __first = _VSTD::find(__first, __last, __value_);
2098    if (__first != __last)
2099    {
2100        _ForwardIterator __i = __first;
2101        while (++__i != __last)
2102        {
2103            if (!(*__i == __value_))
2104            {
2105                *__first = _VSTD::move(*__i);
2106                ++__first;
2107            }
2108        }
2109    }
2110    return __first;
2111}
2112
2113// remove_if
2114
2115template <class _ForwardIterator, class _Predicate>
2116_LIBCPP_NODISCARD_EXT _LIBCPP_CONSTEXPR_AFTER_CXX17 _ForwardIterator
2117remove_if(_ForwardIterator __first, _ForwardIterator __last, _Predicate __pred)
2118{
2119    __first = _VSTD::find_if<_ForwardIterator, typename add_lvalue_reference<_Predicate>::type>
2120                           (__first, __last, __pred);
2121    if (__first != __last)
2122    {
2123        _ForwardIterator __i = __first;
2124        while (++__i != __last)
2125        {
2126            if (!__pred(*__i))
2127            {
2128                *__first = _VSTD::move(*__i);
2129                ++__first;
2130            }
2131        }
2132    }
2133    return __first;
2134}
2135
2136// remove_copy
2137
2138template <class _InputIterator, class _OutputIterator, class _Tp>
2139inline _LIBCPP_INLINE_VISIBILITY _LIBCPP_CONSTEXPR_AFTER_CXX17
2140_OutputIterator
2141remove_copy(_InputIterator __first, _InputIterator __last, _OutputIterator __result, const _Tp& __value_)
2142{
2143    for (; __first != __last; ++__first)
2144    {
2145        if (!(*__first == __value_))
2146        {
2147            *__result = *__first;
2148            ++__result;
2149        }
2150    }
2151    return __result;
2152}
2153
2154// remove_copy_if
2155
2156template <class _InputIterator, class _OutputIterator, class _Predicate>
2157inline _LIBCPP_INLINE_VISIBILITY _LIBCPP_CONSTEXPR_AFTER_CXX17
2158_OutputIterator
2159remove_copy_if(_InputIterator __first, _InputIterator __last, _OutputIterator __result, _Predicate __pred)
2160{
2161    for (; __first != __last; ++__first)
2162    {
2163        if (!__pred(*__first))
2164        {
2165            *__result = *__first;
2166            ++__result;
2167        }
2168    }
2169    return __result;
2170}
2171
2172// unique
2173
2174template <class _ForwardIterator, class _BinaryPredicate>
2175_LIBCPP_NODISCARD_EXT _LIBCPP_CONSTEXPR_AFTER_CXX17 _ForwardIterator
2176unique(_ForwardIterator __first, _ForwardIterator __last, _BinaryPredicate __pred)
2177{
2178    __first = _VSTD::adjacent_find<_ForwardIterator, typename add_lvalue_reference<_BinaryPredicate>::type>
2179                                 (__first, __last, __pred);
2180    if (__first != __last)
2181    {
2182        // ...  a  a  ?  ...
2183        //      f     i
2184        _ForwardIterator __i = __first;
2185        for (++__i; ++__i != __last;)
2186            if (!__pred(*__first, *__i))
2187                *++__first = _VSTD::move(*__i);
2188        ++__first;
2189    }
2190    return __first;
2191}
2192
2193template <class _ForwardIterator>
2194_LIBCPP_NODISCARD_EXT inline
2195_LIBCPP_INLINE_VISIBILITY _LIBCPP_CONSTEXPR_AFTER_CXX17
2196_ForwardIterator
2197unique(_ForwardIterator __first, _ForwardIterator __last)
2198{
2199    typedef typename iterator_traits<_ForwardIterator>::value_type __v;
2200    return _VSTD::unique(__first, __last, __equal_to<__v>());
2201}
2202
2203// unique_copy
2204
2205template <class _BinaryPredicate, class _InputIterator, class _OutputIterator>
2206_LIBCPP_CONSTEXPR_AFTER_CXX17 _OutputIterator
2207__unique_copy(_InputIterator __first, _InputIterator __last, _OutputIterator __result, _BinaryPredicate __pred,
2208              input_iterator_tag, output_iterator_tag)
2209{
2210    if (__first != __last)
2211    {
2212        typename iterator_traits<_InputIterator>::value_type __t(*__first);
2213        *__result = __t;
2214        ++__result;
2215        while (++__first != __last)
2216        {
2217            if (!__pred(__t, *__first))
2218            {
2219                __t = *__first;
2220                *__result = __t;
2221                ++__result;
2222            }
2223        }
2224    }
2225    return __result;
2226}
2227
2228template <class _BinaryPredicate, class _ForwardIterator, class _OutputIterator>
2229_LIBCPP_CONSTEXPR_AFTER_CXX17 _OutputIterator
2230__unique_copy(_ForwardIterator __first, _ForwardIterator __last, _OutputIterator __result, _BinaryPredicate __pred,
2231              forward_iterator_tag, output_iterator_tag)
2232{
2233    if (__first != __last)
2234    {
2235        _ForwardIterator __i = __first;
2236        *__result = *__i;
2237        ++__result;
2238        while (++__first != __last)
2239        {
2240            if (!__pred(*__i, *__first))
2241            {
2242                *__result = *__first;
2243                ++__result;
2244                __i = __first;
2245            }
2246        }
2247    }
2248    return __result;
2249}
2250
2251template <class _BinaryPredicate, class _InputIterator, class _ForwardIterator>
2252_LIBCPP_CONSTEXPR_AFTER_CXX17 _ForwardIterator
2253__unique_copy(_InputIterator __first, _InputIterator __last, _ForwardIterator __result, _BinaryPredicate __pred,
2254              input_iterator_tag, forward_iterator_tag)
2255{
2256    if (__first != __last)
2257    {
2258        *__result = *__first;
2259        while (++__first != __last)
2260            if (!__pred(*__result, *__first))
2261                *++__result = *__first;
2262        ++__result;
2263    }
2264    return __result;
2265}
2266
2267template <class _InputIterator, class _OutputIterator, class _BinaryPredicate>
2268inline _LIBCPP_INLINE_VISIBILITY _LIBCPP_CONSTEXPR_AFTER_CXX17
2269_OutputIterator
2270unique_copy(_InputIterator __first, _InputIterator __last, _OutputIterator __result, _BinaryPredicate __pred)
2271{
2272    return _VSTD::__unique_copy<typename add_lvalue_reference<_BinaryPredicate>::type>
2273                              (__first, __last, __result, __pred,
2274                               typename iterator_traits<_InputIterator>::iterator_category(),
2275                               typename iterator_traits<_OutputIterator>::iterator_category());
2276}
2277
2278template <class _InputIterator, class _OutputIterator>
2279inline _LIBCPP_INLINE_VISIBILITY _LIBCPP_CONSTEXPR_AFTER_CXX17
2280_OutputIterator
2281unique_copy(_InputIterator __first, _InputIterator __last, _OutputIterator __result)
2282{
2283    typedef typename iterator_traits<_InputIterator>::value_type __v;
2284    return _VSTD::unique_copy(__first, __last, __result, __equal_to<__v>());
2285}
2286
2287// reverse
2288
2289template <class _BidirectionalIterator>
2290inline _LIBCPP_INLINE_VISIBILITY
2291void
2292__reverse(_BidirectionalIterator __first, _BidirectionalIterator __last, bidirectional_iterator_tag)
2293{
2294    while (__first != __last)
2295    {
2296        if (__first == --__last)
2297            break;
2298        _VSTD::iter_swap(__first, __last);
2299        ++__first;
2300    }
2301}
2302
2303template <class _RandomAccessIterator>
2304inline _LIBCPP_INLINE_VISIBILITY
2305void
2306__reverse(_RandomAccessIterator __first, _RandomAccessIterator __last, random_access_iterator_tag)
2307{
2308    if (__first != __last)
2309        for (; __first < --__last; ++__first)
2310            _VSTD::iter_swap(__first, __last);
2311}
2312
2313template <class _BidirectionalIterator>
2314inline _LIBCPP_INLINE_VISIBILITY
2315void
2316reverse(_BidirectionalIterator __first, _BidirectionalIterator __last)
2317{
2318    _VSTD::__reverse(__first, __last, typename iterator_traits<_BidirectionalIterator>::iterator_category());
2319}
2320
2321// reverse_copy
2322
2323template <class _BidirectionalIterator, class _OutputIterator>
2324inline _LIBCPP_INLINE_VISIBILITY _LIBCPP_CONSTEXPR_AFTER_CXX17
2325_OutputIterator
2326reverse_copy(_BidirectionalIterator __first, _BidirectionalIterator __last, _OutputIterator __result)
2327{
2328    for (; __first != __last; ++__result)
2329        *__result = *--__last;
2330    return __result;
2331}
2332
2333// rotate
2334
2335template <class _ForwardIterator>
2336_ForwardIterator
2337__rotate_left(_ForwardIterator __first, _ForwardIterator __last)
2338{
2339    typedef typename iterator_traits<_ForwardIterator>::value_type value_type;
2340    value_type __tmp = _VSTD::move(*__first);
2341    _ForwardIterator __lm1 = _VSTD::move(_VSTD::next(__first), __last, __first);
2342    *__lm1 = _VSTD::move(__tmp);
2343    return __lm1;
2344}
2345
2346template <class _BidirectionalIterator>
2347_BidirectionalIterator
2348__rotate_right(_BidirectionalIterator __first, _BidirectionalIterator __last)
2349{
2350    typedef typename iterator_traits<_BidirectionalIterator>::value_type value_type;
2351    _BidirectionalIterator __lm1 = _VSTD::prev(__last);
2352    value_type __tmp = _VSTD::move(*__lm1);
2353    _BidirectionalIterator __fp1 = _VSTD::move_backward(__first, __lm1, __last);
2354    *__first = _VSTD::move(__tmp);
2355    return __fp1;
2356}
2357
2358template <class _ForwardIterator>
2359_ForwardIterator
2360__rotate_forward(_ForwardIterator __first, _ForwardIterator __middle, _ForwardIterator __last)
2361{
2362    _ForwardIterator __i = __middle;
2363    while (true)
2364    {
2365        swap(*__first, *__i);
2366        ++__first;
2367        if (++__i == __last)
2368            break;
2369        if (__first == __middle)
2370            __middle = __i;
2371    }
2372    _ForwardIterator __r = __first;
2373    if (__first != __middle)
2374    {
2375        __i = __middle;
2376        while (true)
2377        {
2378            swap(*__first, *__i);
2379            ++__first;
2380            if (++__i == __last)
2381            {
2382                if (__first == __middle)
2383                    break;
2384                __i = __middle;
2385            }
2386            else if (__first == __middle)
2387                __middle = __i;
2388        }
2389    }
2390    return __r;
2391}
2392
2393template<typename _Integral>
2394inline _LIBCPP_INLINE_VISIBILITY
2395_Integral
2396__algo_gcd(_Integral __x, _Integral __y)
2397{
2398    do
2399    {
2400        _Integral __t = __x % __y;
2401        __x = __y;
2402        __y = __t;
2403    } while (__y);
2404    return __x;
2405}
2406
2407template<typename _RandomAccessIterator>
2408_RandomAccessIterator
2409__rotate_gcd(_RandomAccessIterator __first, _RandomAccessIterator __middle, _RandomAccessIterator __last)
2410{
2411    typedef typename iterator_traits<_RandomAccessIterator>::difference_type difference_type;
2412    typedef typename iterator_traits<_RandomAccessIterator>::value_type value_type;
2413
2414    const difference_type __m1 = __middle - __first;
2415    const difference_type __m2 = __last - __middle;
2416    if (__m1 == __m2)
2417    {
2418        _VSTD::swap_ranges(__first, __middle, __middle);
2419        return __middle;
2420    }
2421    const difference_type __g = _VSTD::__algo_gcd(__m1, __m2);
2422    for (_RandomAccessIterator __p = __first + __g; __p != __first;)
2423    {
2424        value_type __t(_VSTD::move(*--__p));
2425        _RandomAccessIterator __p1 = __p;
2426        _RandomAccessIterator __p2 = __p1 + __m1;
2427        do
2428        {
2429            *__p1 = _VSTD::move(*__p2);
2430            __p1 = __p2;
2431            const difference_type __d = __last - __p2;
2432            if (__m1 < __d)
2433                __p2 += __m1;
2434            else
2435                __p2 = __first + (__m1 - __d);
2436        } while (__p2 != __p);
2437        *__p1 = _VSTD::move(__t);
2438    }
2439    return __first + __m2;
2440}
2441
2442template <class _ForwardIterator>
2443inline _LIBCPP_INLINE_VISIBILITY
2444_ForwardIterator
2445__rotate(_ForwardIterator __first, _ForwardIterator __middle, _ForwardIterator __last,
2446         _VSTD::forward_iterator_tag)
2447{
2448    typedef typename _VSTD::iterator_traits<_ForwardIterator>::value_type value_type;
2449    if (_VSTD::is_trivially_move_assignable<value_type>::value)
2450    {
2451        if (_VSTD::next(__first) == __middle)
2452            return _VSTD::__rotate_left(__first, __last);
2453    }
2454    return _VSTD::__rotate_forward(__first, __middle, __last);
2455}
2456
2457template <class _BidirectionalIterator>
2458inline _LIBCPP_INLINE_VISIBILITY
2459_BidirectionalIterator
2460__rotate(_BidirectionalIterator __first, _BidirectionalIterator __middle, _BidirectionalIterator __last,
2461         _VSTD::bidirectional_iterator_tag)
2462{
2463    typedef typename _VSTD::iterator_traits<_BidirectionalIterator>::value_type value_type;
2464    if (_VSTD::is_trivially_move_assignable<value_type>::value)
2465    {
2466        if (_VSTD::next(__first) == __middle)
2467            return _VSTD::__rotate_left(__first, __last);
2468        if (_VSTD::next(__middle) == __last)
2469            return _VSTD::__rotate_right(__first, __last);
2470    }
2471    return _VSTD::__rotate_forward(__first, __middle, __last);
2472}
2473
2474template <class _RandomAccessIterator>
2475inline _LIBCPP_INLINE_VISIBILITY
2476_RandomAccessIterator
2477__rotate(_RandomAccessIterator __first, _RandomAccessIterator __middle, _RandomAccessIterator __last,
2478         _VSTD::random_access_iterator_tag)
2479{
2480    typedef typename _VSTD::iterator_traits<_RandomAccessIterator>::value_type value_type;
2481    if (_VSTD::is_trivially_move_assignable<value_type>::value)
2482    {
2483        if (_VSTD::next(__first) == __middle)
2484            return _VSTD::__rotate_left(__first, __last);
2485        if (_VSTD::next(__middle) == __last)
2486            return _VSTD::__rotate_right(__first, __last);
2487        return _VSTD::__rotate_gcd(__first, __middle, __last);
2488    }
2489    return _VSTD::__rotate_forward(__first, __middle, __last);
2490}
2491
2492template <class _ForwardIterator>
2493inline _LIBCPP_INLINE_VISIBILITY
2494_ForwardIterator
2495rotate(_ForwardIterator __first, _ForwardIterator __middle, _ForwardIterator __last)
2496{
2497    if (__first == __middle)
2498        return __last;
2499    if (__middle == __last)
2500        return __first;
2501    return _VSTD::__rotate(__first, __middle, __last,
2502                           typename _VSTD::iterator_traits<_ForwardIterator>::iterator_category());
2503}
2504
2505// rotate_copy
2506
2507template <class _ForwardIterator, class _OutputIterator>
2508inline _LIBCPP_INLINE_VISIBILITY
2509_OutputIterator
2510rotate_copy(_ForwardIterator __first, _ForwardIterator __middle, _ForwardIterator __last, _OutputIterator __result)
2511{
2512    return _VSTD::copy(__first, __middle, _VSTD::copy(__middle, __last, __result));
2513}
2514
2515// min_element
2516
2517template <class _ForwardIterator, class _Compare>
2518_LIBCPP_NODISCARD_EXT inline
2519_LIBCPP_INLINE_VISIBILITY _LIBCPP_CONSTEXPR_AFTER_CXX11
2520_ForwardIterator
2521min_element(_ForwardIterator __first, _ForwardIterator __last, _Compare __comp)
2522{
2523    static_assert(__is_cpp17_forward_iterator<_ForwardIterator>::value,
2524        "std::min_element requires a ForwardIterator");
2525    if (__first != __last)
2526    {
2527        _ForwardIterator __i = __first;
2528        while (++__i != __last)
2529            if (__comp(*__i, *__first))
2530                __first = __i;
2531    }
2532    return __first;
2533}
2534
2535template <class _ForwardIterator>
2536_LIBCPP_NODISCARD_EXT inline
2537_LIBCPP_INLINE_VISIBILITY _LIBCPP_CONSTEXPR_AFTER_CXX11
2538_ForwardIterator
2539min_element(_ForwardIterator __first, _ForwardIterator __last)
2540{
2541    return _VSTD::min_element(__first, __last,
2542              __less<typename iterator_traits<_ForwardIterator>::value_type>());
2543}
2544
2545// min
2546
2547template <class _Tp, class _Compare>
2548_LIBCPP_NODISCARD_EXT inline
2549_LIBCPP_INLINE_VISIBILITY _LIBCPP_CONSTEXPR_AFTER_CXX11
2550const _Tp&
2551min(const _Tp& __a, const _Tp& __b, _Compare __comp)
2552{
2553    return __comp(__b, __a) ? __b : __a;
2554}
2555
2556template <class _Tp>
2557_LIBCPP_NODISCARD_EXT inline
2558_LIBCPP_INLINE_VISIBILITY _LIBCPP_CONSTEXPR_AFTER_CXX11
2559const _Tp&
2560min(const _Tp& __a, const _Tp& __b)
2561{
2562    return _VSTD::min(__a, __b, __less<_Tp>());
2563}
2564
2565#ifndef _LIBCPP_CXX03_LANG
2566
2567template<class _Tp, class _Compare>
2568_LIBCPP_NODISCARD_EXT inline
2569_LIBCPP_INLINE_VISIBILITY _LIBCPP_CONSTEXPR_AFTER_CXX11
2570_Tp
2571min(initializer_list<_Tp> __t, _Compare __comp)
2572{
2573    return *_VSTD::min_element(__t.begin(), __t.end(), __comp);
2574}
2575
2576template<class _Tp>
2577_LIBCPP_NODISCARD_EXT inline
2578_LIBCPP_INLINE_VISIBILITY _LIBCPP_CONSTEXPR_AFTER_CXX11
2579_Tp
2580min(initializer_list<_Tp> __t)
2581{
2582    return *_VSTD::min_element(__t.begin(), __t.end(), __less<_Tp>());
2583}
2584
2585#endif  // _LIBCPP_CXX03_LANG
2586
2587// max_element
2588
2589template <class _ForwardIterator, class _Compare>
2590_LIBCPP_NODISCARD_EXT inline
2591_LIBCPP_INLINE_VISIBILITY _LIBCPP_CONSTEXPR_AFTER_CXX11
2592_ForwardIterator
2593max_element(_ForwardIterator __first, _ForwardIterator __last, _Compare __comp)
2594{
2595    static_assert(__is_cpp17_forward_iterator<_ForwardIterator>::value,
2596        "std::max_element requires a ForwardIterator");
2597    if (__first != __last)
2598    {
2599        _ForwardIterator __i = __first;
2600        while (++__i != __last)
2601            if (__comp(*__first, *__i))
2602                __first = __i;
2603    }
2604    return __first;
2605}
2606
2607
2608template <class _ForwardIterator>
2609_LIBCPP_NODISCARD_EXT inline
2610_LIBCPP_INLINE_VISIBILITY _LIBCPP_CONSTEXPR_AFTER_CXX11
2611_ForwardIterator
2612max_element(_ForwardIterator __first, _ForwardIterator __last)
2613{
2614    return _VSTD::max_element(__first, __last,
2615              __less<typename iterator_traits<_ForwardIterator>::value_type>());
2616}
2617
2618// max
2619
2620template <class _Tp, class _Compare>
2621_LIBCPP_NODISCARD_EXT inline
2622_LIBCPP_INLINE_VISIBILITY _LIBCPP_CONSTEXPR_AFTER_CXX11
2623const _Tp&
2624max(const _Tp& __a, const _Tp& __b, _Compare __comp)
2625{
2626    return __comp(__a, __b) ? __b : __a;
2627}
2628
2629template <class _Tp>
2630_LIBCPP_NODISCARD_EXT inline
2631_LIBCPP_INLINE_VISIBILITY _LIBCPP_CONSTEXPR_AFTER_CXX11
2632const _Tp&
2633max(const _Tp& __a, const _Tp& __b)
2634{
2635    return _VSTD::max(__a, __b, __less<_Tp>());
2636}
2637
2638#ifndef _LIBCPP_CXX03_LANG
2639
2640template<class _Tp, class _Compare>
2641_LIBCPP_NODISCARD_EXT inline
2642_LIBCPP_INLINE_VISIBILITY _LIBCPP_CONSTEXPR_AFTER_CXX11
2643_Tp
2644max(initializer_list<_Tp> __t, _Compare __comp)
2645{
2646    return *_VSTD::max_element(__t.begin(), __t.end(), __comp);
2647}
2648
2649template<class _Tp>
2650_LIBCPP_NODISCARD_EXT inline
2651_LIBCPP_INLINE_VISIBILITY _LIBCPP_CONSTEXPR_AFTER_CXX11
2652_Tp
2653max(initializer_list<_Tp> __t)
2654{
2655    return *_VSTD::max_element(__t.begin(), __t.end(), __less<_Tp>());
2656}
2657
2658#endif  // _LIBCPP_CXX03_LANG
2659
2660#if _LIBCPP_STD_VER > 14
2661// clamp
2662template<class _Tp, class _Compare>
2663_LIBCPP_NODISCARD_EXT inline
2664_LIBCPP_INLINE_VISIBILITY _LIBCPP_CONSTEXPR
2665const _Tp&
2666clamp(const _Tp& __v, const _Tp& __lo, const _Tp& __hi, _Compare __comp)
2667{
2668    _LIBCPP_ASSERT(!__comp(__hi, __lo), "Bad bounds passed to std::clamp");
2669    return __comp(__v, __lo) ? __lo : __comp(__hi, __v) ? __hi : __v;
2670
2671}
2672
2673template<class _Tp>
2674_LIBCPP_NODISCARD_EXT inline
2675_LIBCPP_INLINE_VISIBILITY _LIBCPP_CONSTEXPR
2676const _Tp&
2677clamp(const _Tp& __v, const _Tp& __lo, const _Tp& __hi)
2678{
2679    return _VSTD::clamp(__v, __lo, __hi, __less<_Tp>());
2680}
2681#endif
2682
2683// minmax_element
2684
2685template <class _ForwardIterator, class _Compare>
2686_LIBCPP_NODISCARD_EXT _LIBCPP_CONSTEXPR_AFTER_CXX11
2687std::pair<_ForwardIterator, _ForwardIterator>
2688minmax_element(_ForwardIterator __first, _ForwardIterator __last, _Compare __comp)
2689{
2690  static_assert(__is_cpp17_forward_iterator<_ForwardIterator>::value,
2691        "std::minmax_element requires a ForwardIterator");
2692  std::pair<_ForwardIterator, _ForwardIterator> __result(__first, __first);
2693  if (__first != __last)
2694  {
2695      if (++__first != __last)
2696      {
2697          if (__comp(*__first, *__result.first))
2698              __result.first = __first;
2699          else
2700              __result.second = __first;
2701          while (++__first != __last)
2702          {
2703              _ForwardIterator __i = __first;
2704              if (++__first == __last)
2705              {
2706                  if (__comp(*__i, *__result.first))
2707                      __result.first = __i;
2708                  else if (!__comp(*__i, *__result.second))
2709                      __result.second = __i;
2710                  break;
2711              }
2712              else
2713              {
2714                  if (__comp(*__first, *__i))
2715                  {
2716                      if (__comp(*__first, *__result.first))
2717                          __result.first = __first;
2718                      if (!__comp(*__i, *__result.second))
2719                          __result.second = __i;
2720                  }
2721                  else
2722                  {
2723                      if (__comp(*__i, *__result.first))
2724                          __result.first = __i;
2725                      if (!__comp(*__first, *__result.second))
2726                          __result.second = __first;
2727                  }
2728              }
2729          }
2730      }
2731  }
2732  return __result;
2733}
2734
2735template <class _ForwardIterator>
2736_LIBCPP_NODISCARD_EXT inline
2737_LIBCPP_INLINE_VISIBILITY _LIBCPP_CONSTEXPR_AFTER_CXX11
2738std::pair<_ForwardIterator, _ForwardIterator>
2739minmax_element(_ForwardIterator __first, _ForwardIterator __last)
2740{
2741    return _VSTD::minmax_element(__first, __last,
2742              __less<typename iterator_traits<_ForwardIterator>::value_type>());
2743}
2744
2745// minmax
2746
2747template<class _Tp, class _Compare>
2748_LIBCPP_NODISCARD_EXT inline
2749_LIBCPP_INLINE_VISIBILITY _LIBCPP_CONSTEXPR_AFTER_CXX11
2750pair<const _Tp&, const _Tp&>
2751minmax(const _Tp& __a, const _Tp& __b, _Compare __comp)
2752{
2753    return __comp(__b, __a) ? pair<const _Tp&, const _Tp&>(__b, __a) :
2754                              pair<const _Tp&, const _Tp&>(__a, __b);
2755}
2756
2757template<class _Tp>
2758_LIBCPP_NODISCARD_EXT inline
2759_LIBCPP_INLINE_VISIBILITY _LIBCPP_CONSTEXPR_AFTER_CXX11
2760pair<const _Tp&, const _Tp&>
2761minmax(const _Tp& __a, const _Tp& __b)
2762{
2763    return _VSTD::minmax(__a, __b, __less<_Tp>());
2764}
2765
2766#ifndef _LIBCPP_CXX03_LANG
2767
2768template<class _Tp, class _Compare>
2769_LIBCPP_NODISCARD_EXT inline
2770_LIBCPP_INLINE_VISIBILITY _LIBCPP_CONSTEXPR_AFTER_CXX11
2771pair<_Tp, _Tp>
2772minmax(initializer_list<_Tp> __t, _Compare __comp)
2773{
2774    typedef typename initializer_list<_Tp>::const_iterator _Iter;
2775    _Iter __first = __t.begin();
2776    _Iter __last  = __t.end();
2777    std::pair<_Tp, _Tp> __result(*__first, *__first);
2778
2779    ++__first;
2780    if (__t.size() % 2 == 0)
2781    {
2782        if (__comp(*__first,  __result.first))
2783            __result.first  = *__first;
2784        else
2785            __result.second = *__first;
2786        ++__first;
2787    }
2788
2789    while (__first != __last)
2790    {
2791        _Tp __prev = *__first++;
2792        if (__comp(*__first, __prev)) {
2793            if ( __comp(*__first, __result.first)) __result.first  = *__first;
2794            if (!__comp(__prev, __result.second))  __result.second = __prev;
2795            }
2796        else {
2797            if ( __comp(__prev, __result.first))    __result.first  = __prev;
2798            if (!__comp(*__first, __result.second)) __result.second = *__first;
2799            }
2800
2801        __first++;
2802    }
2803    return __result;
2804}
2805
2806template<class _Tp>
2807_LIBCPP_NODISCARD_EXT inline
2808_LIBCPP_INLINE_VISIBILITY _LIBCPP_CONSTEXPR_AFTER_CXX11
2809pair<_Tp, _Tp>
2810minmax(initializer_list<_Tp> __t)
2811{
2812    return _VSTD::minmax(__t, __less<_Tp>());
2813}
2814
2815#endif  // _LIBCPP_CXX03_LANG
2816
2817// random_shuffle
2818
2819// __independent_bits_engine
2820
2821template <unsigned long long _Xp, size_t _Rp>
2822struct __log2_imp
2823{
2824    static const size_t value = _Xp & ((unsigned long long)(1) << _Rp) ? _Rp
2825                                           : __log2_imp<_Xp, _Rp - 1>::value;
2826};
2827
2828template <unsigned long long _Xp>
2829struct __log2_imp<_Xp, 0>
2830{
2831    static const size_t value = 0;
2832};
2833
2834template <size_t _Rp>
2835struct __log2_imp<0, _Rp>
2836{
2837    static const size_t value = _Rp + 1;
2838};
2839
2840template <class _UIntType, _UIntType _Xp>
2841struct __log2
2842{
2843    static const size_t value = __log2_imp<_Xp,
2844                                         sizeof(_UIntType) * __CHAR_BIT__ - 1>::value;
2845};
2846
2847template<class _Engine, class _UIntType>
2848class __independent_bits_engine
2849{
2850public:
2851    // types
2852    typedef _UIntType result_type;
2853
2854private:
2855    typedef typename _Engine::result_type _Engine_result_type;
2856    typedef typename conditional
2857        <
2858            sizeof(_Engine_result_type) <= sizeof(result_type),
2859                result_type,
2860                _Engine_result_type
2861        >::type _Working_result_type;
2862
2863    _Engine& __e_;
2864    size_t __w_;
2865    size_t __w0_;
2866    size_t __n_;
2867    size_t __n0_;
2868    _Working_result_type __y0_;
2869    _Working_result_type __y1_;
2870    _Engine_result_type __mask0_;
2871    _Engine_result_type __mask1_;
2872
2873#ifdef _LIBCPP_CXX03_LANG
2874    static const _Working_result_type _Rp = _Engine::_Max - _Engine::_Min
2875                                          + _Working_result_type(1);
2876#else
2877    static _LIBCPP_CONSTEXPR const _Working_result_type _Rp = _Engine::max() - _Engine::min()
2878                                                      + _Working_result_type(1);
2879#endif
2880    static _LIBCPP_CONSTEXPR const size_t __m = __log2<_Working_result_type, _Rp>::value;
2881    static _LIBCPP_CONSTEXPR const size_t _WDt = numeric_limits<_Working_result_type>::digits;
2882    static _LIBCPP_CONSTEXPR const size_t _EDt = numeric_limits<_Engine_result_type>::digits;
2883
2884public:
2885    // constructors and seeding functions
2886    __independent_bits_engine(_Engine& __e, size_t __w);
2887
2888    // generating functions
2889    result_type operator()() {return __eval(integral_constant<bool, _Rp != 0>());}
2890
2891private:
2892    result_type __eval(false_type);
2893    result_type __eval(true_type);
2894};
2895
2896template<class _Engine, class _UIntType>
2897__independent_bits_engine<_Engine, _UIntType>
2898    ::__independent_bits_engine(_Engine& __e, size_t __w)
2899        : __e_(__e),
2900          __w_(__w)
2901{
2902    __n_ = __w_ / __m + (__w_ % __m != 0);
2903    __w0_ = __w_ / __n_;
2904    if (_Rp == 0)
2905        __y0_ = _Rp;
2906    else if (__w0_ < _WDt)
2907        __y0_ = (_Rp >> __w0_) << __w0_;
2908    else
2909        __y0_ = 0;
2910    if (_Rp - __y0_ > __y0_ / __n_)
2911    {
2912        ++__n_;
2913        __w0_ = __w_ / __n_;
2914        if (__w0_ < _WDt)
2915            __y0_ = (_Rp >> __w0_) << __w0_;
2916        else
2917            __y0_ = 0;
2918    }
2919    __n0_ = __n_ - __w_ % __n_;
2920    if (__w0_ < _WDt - 1)
2921        __y1_ = (_Rp >> (__w0_ + 1)) << (__w0_ + 1);
2922    else
2923        __y1_ = 0;
2924    __mask0_ = __w0_ > 0 ? _Engine_result_type(~0) >> (_EDt - __w0_) :
2925                          _Engine_result_type(0);
2926    __mask1_ = __w0_ < _EDt - 1 ?
2927                               _Engine_result_type(~0) >> (_EDt - (__w0_ + 1)) :
2928                               _Engine_result_type(~0);
2929}
2930
2931template<class _Engine, class _UIntType>
2932inline
2933_UIntType
2934__independent_bits_engine<_Engine, _UIntType>::__eval(false_type)
2935{
2936    return static_cast<result_type>(__e_() & __mask0_);
2937}
2938
2939template<class _Engine, class _UIntType>
2940_UIntType
2941__independent_bits_engine<_Engine, _UIntType>::__eval(true_type)
2942{
2943    const size_t _WRt = numeric_limits<result_type>::digits;
2944    result_type _Sp = 0;
2945    for (size_t __k = 0; __k < __n0_; ++__k)
2946    {
2947        _Engine_result_type __u;
2948        do
2949        {
2950            __u = __e_() - _Engine::min();
2951        } while (__u >= __y0_);
2952        if (__w0_ < _WRt)
2953            _Sp <<= __w0_;
2954        else
2955            _Sp = 0;
2956        _Sp += __u & __mask0_;
2957    }
2958    for (size_t __k = __n0_; __k < __n_; ++__k)
2959    {
2960        _Engine_result_type __u;
2961        do
2962        {
2963            __u = __e_() - _Engine::min();
2964        } while (__u >= __y1_);
2965        if (__w0_ < _WRt - 1)
2966            _Sp <<= __w0_ + 1;
2967        else
2968            _Sp = 0;
2969        _Sp += __u & __mask1_;
2970    }
2971    return _Sp;
2972}
2973
2974// uniform_int_distribution
2975
2976template<class _IntType = int>
2977class uniform_int_distribution
2978{
2979public:
2980    // types
2981    typedef _IntType result_type;
2982
2983    class param_type
2984    {
2985        result_type __a_;
2986        result_type __b_;
2987    public:
2988        typedef uniform_int_distribution distribution_type;
2989
2990        explicit param_type(result_type __a = 0,
2991                            result_type __b = numeric_limits<result_type>::max())
2992            : __a_(__a), __b_(__b) {}
2993
2994        result_type a() const {return __a_;}
2995        result_type b() const {return __b_;}
2996
2997        friend bool operator==(const param_type& __x, const param_type& __y)
2998            {return __x.__a_ == __y.__a_ && __x.__b_ == __y.__b_;}
2999        friend bool operator!=(const param_type& __x, const param_type& __y)
3000            {return !(__x == __y);}
3001    };
3002
3003private:
3004    param_type __p_;
3005
3006public:
3007    // constructors and reset functions
3008    explicit uniform_int_distribution(result_type __a = 0,
3009                                      result_type __b = numeric_limits<result_type>::max())
3010        : __p_(param_type(__a, __b)) {}
3011    explicit uniform_int_distribution(const param_type& __p) : __p_(__p) {}
3012    void reset() {}
3013
3014    // generating functions
3015    template<class _URNG> result_type operator()(_URNG& __g)
3016        {return (*this)(__g, __p_);}
3017    template<class _URNG> result_type operator()(_URNG& __g, const param_type& __p);
3018
3019    // property functions
3020    result_type a() const {return __p_.a();}
3021    result_type b() const {return __p_.b();}
3022
3023    param_type param() const {return __p_;}
3024    void param(const param_type& __p) {__p_ = __p;}
3025
3026    result_type min() const {return a();}
3027    result_type max() const {return b();}
3028
3029    friend bool operator==(const uniform_int_distribution& __x,
3030                           const uniform_int_distribution& __y)
3031        {return __x.__p_ == __y.__p_;}
3032    friend bool operator!=(const uniform_int_distribution& __x,
3033                           const uniform_int_distribution& __y)
3034            {return !(__x == __y);}
3035};
3036
3037template<class _IntType>
3038template<class _URNG>
3039typename uniform_int_distribution<_IntType>::result_type
3040uniform_int_distribution<_IntType>::operator()(_URNG& __g, const param_type& __p)
3041_LIBCPP_DISABLE_UBSAN_UNSIGNED_INTEGER_CHECK
3042{
3043    typedef typename conditional<sizeof(result_type) <= sizeof(uint32_t),
3044                                            uint32_t, uint64_t>::type _UIntType;
3045    const _UIntType _Rp = _UIntType(__p.b()) - _UIntType(__p.a()) + _UIntType(1);
3046    if (_Rp == 1)
3047        return __p.a();
3048    const size_t _Dt = numeric_limits<_UIntType>::digits;
3049    typedef __independent_bits_engine<_URNG, _UIntType> _Eng;
3050    if (_Rp == 0)
3051        return static_cast<result_type>(_Eng(__g, _Dt)());
3052    size_t __w = _Dt - __libcpp_clz(_Rp) - 1;
3053    if ((_Rp & (std::numeric_limits<_UIntType>::max() >> (_Dt - __w))) != 0)
3054        ++__w;
3055    _Eng __e(__g, __w);
3056    _UIntType __u;
3057    do
3058    {
3059        __u = __e();
3060    } while (__u >= _Rp);
3061    return static_cast<result_type>(__u + __p.a());
3062}
3063
3064#if _LIBCPP_STD_VER <= 14 || defined(_LIBCPP_ENABLE_CXX17_REMOVED_RANDOM_SHUFFLE) \
3065  || defined(_LIBCPP_BUILDING_LIBRARY)
3066class _LIBCPP_TYPE_VIS __rs_default;
3067
3068_LIBCPP_FUNC_VIS __rs_default __rs_get();
3069
3070class _LIBCPP_TYPE_VIS __rs_default
3071{
3072    static unsigned __c_;
3073
3074    __rs_default();
3075public:
3076    typedef uint_fast32_t result_type;
3077
3078    static const result_type _Min = 0;
3079    static const result_type _Max = 0xFFFFFFFF;
3080
3081    __rs_default(const __rs_default&);
3082    ~__rs_default();
3083
3084    result_type operator()();
3085
3086    static _LIBCPP_CONSTEXPR result_type min() {return _Min;}
3087    static _LIBCPP_CONSTEXPR result_type max() {return _Max;}
3088
3089    friend _LIBCPP_FUNC_VIS __rs_default __rs_get();
3090};
3091
3092_LIBCPP_FUNC_VIS __rs_default __rs_get();
3093
3094template <class _RandomAccessIterator>
3095_LIBCPP_DEPRECATED_IN_CXX14 void
3096random_shuffle(_RandomAccessIterator __first, _RandomAccessIterator __last)
3097{
3098    typedef typename iterator_traits<_RandomAccessIterator>::difference_type difference_type;
3099    typedef uniform_int_distribution<ptrdiff_t> _Dp;
3100    typedef typename _Dp::param_type _Pp;
3101    difference_type __d = __last - __first;
3102    if (__d > 1)
3103    {
3104        _Dp __uid;
3105        __rs_default __g = __rs_get();
3106        for (--__last, (void) --__d; __first < __last; ++__first, (void) --__d)
3107        {
3108            difference_type __i = __uid(__g, _Pp(0, __d));
3109            if (__i != difference_type(0))
3110                swap(*__first, *(__first + __i));
3111        }
3112    }
3113}
3114
3115template <class _RandomAccessIterator, class _RandomNumberGenerator>
3116_LIBCPP_DEPRECATED_IN_CXX14 void
3117random_shuffle(_RandomAccessIterator __first, _RandomAccessIterator __last,
3118#ifndef _LIBCPP_CXX03_LANG
3119               _RandomNumberGenerator&& __rand)
3120#else
3121               _RandomNumberGenerator& __rand)
3122#endif
3123{
3124    typedef typename iterator_traits<_RandomAccessIterator>::difference_type difference_type;
3125    difference_type __d = __last - __first;
3126    if (__d > 1)
3127    {
3128        for (--__last; __first < __last; ++__first, (void) --__d)
3129        {
3130            difference_type __i = __rand(__d);
3131            if (__i != difference_type(0))
3132              swap(*__first, *(__first + __i));
3133        }
3134    }
3135}
3136#endif
3137
3138template <class _PopulationIterator, class _SampleIterator, class _Distance,
3139          class _UniformRandomNumberGenerator>
3140_LIBCPP_INLINE_VISIBILITY
3141_SampleIterator __sample(_PopulationIterator __first,
3142                         _PopulationIterator __last, _SampleIterator __output_iter,
3143                         _Distance __n,
3144                         _UniformRandomNumberGenerator & __g,
3145                         input_iterator_tag) {
3146
3147  _Distance __k = 0;
3148  for (; __first != __last && __k < __n; ++__first, (void) ++__k)
3149    __output_iter[__k] = *__first;
3150  _Distance __sz = __k;
3151  for (; __first != __last; ++__first, (void) ++__k) {
3152    _Distance __r = _VSTD::uniform_int_distribution<_Distance>(0, __k)(__g);
3153    if (__r < __sz)
3154      __output_iter[__r] = *__first;
3155  }
3156  return __output_iter + _VSTD::min(__n, __k);
3157}
3158
3159template <class _PopulationIterator, class _SampleIterator, class _Distance,
3160          class _UniformRandomNumberGenerator>
3161_LIBCPP_INLINE_VISIBILITY
3162_SampleIterator __sample(_PopulationIterator __first,
3163                         _PopulationIterator __last, _SampleIterator __output_iter,
3164                         _Distance __n,
3165                         _UniformRandomNumberGenerator& __g,
3166                         forward_iterator_tag) {
3167  _Distance __unsampled_sz = _VSTD::distance(__first, __last);
3168  for (__n = _VSTD::min(__n, __unsampled_sz); __n != 0; ++__first) {
3169    _Distance __r =
3170        _VSTD::uniform_int_distribution<_Distance>(0, --__unsampled_sz)(__g);
3171    if (__r < __n) {
3172      *__output_iter++ = *__first;
3173      --__n;
3174    }
3175  }
3176  return __output_iter;
3177}
3178
3179template <class _PopulationIterator, class _SampleIterator, class _Distance,
3180          class _UniformRandomNumberGenerator>
3181_LIBCPP_INLINE_VISIBILITY
3182_SampleIterator __sample(_PopulationIterator __first,
3183                         _PopulationIterator __last, _SampleIterator __output_iter,
3184                         _Distance __n, _UniformRandomNumberGenerator& __g) {
3185  typedef typename iterator_traits<_PopulationIterator>::iterator_category
3186        _PopCategory;
3187  typedef typename iterator_traits<_PopulationIterator>::difference_type
3188        _Difference;
3189  static_assert(__is_cpp17_forward_iterator<_PopulationIterator>::value ||
3190                __is_cpp17_random_access_iterator<_SampleIterator>::value,
3191                "SampleIterator must meet the requirements of RandomAccessIterator");
3192  typedef typename common_type<_Distance, _Difference>::type _CommonType;
3193  _LIBCPP_ASSERT(__n >= 0, "N must be a positive number.");
3194  return _VSTD::__sample(
3195      __first, __last, __output_iter, _CommonType(__n),
3196      __g, _PopCategory());
3197}
3198
3199#if _LIBCPP_STD_VER > 14
3200template <class _PopulationIterator, class _SampleIterator, class _Distance,
3201          class _UniformRandomNumberGenerator>
3202inline _LIBCPP_INLINE_VISIBILITY
3203_SampleIterator sample(_PopulationIterator __first,
3204                       _PopulationIterator __last, _SampleIterator __output_iter,
3205                       _Distance __n, _UniformRandomNumberGenerator&& __g) {
3206    return _VSTD::__sample(__first, __last, __output_iter, __n, __g);
3207}
3208#endif // _LIBCPP_STD_VER > 14
3209
3210template<class _RandomAccessIterator, class _UniformRandomNumberGenerator>
3211    void shuffle(_RandomAccessIterator __first, _RandomAccessIterator __last,
3212                 _UniformRandomNumberGenerator&& __g)
3213{
3214    typedef typename iterator_traits<_RandomAccessIterator>::difference_type difference_type;
3215    typedef uniform_int_distribution<ptrdiff_t> _Dp;
3216    typedef typename _Dp::param_type _Pp;
3217    difference_type __d = __last - __first;
3218    if (__d > 1)
3219    {
3220        _Dp __uid;
3221        for (--__last, (void) --__d; __first < __last; ++__first, (void) --__d)
3222        {
3223            difference_type __i = __uid(__g, _Pp(0, __d));
3224            if (__i != difference_type(0))
3225                swap(*__first, *(__first + __i));
3226        }
3227    }
3228}
3229
3230template <class _InputIterator, class _Predicate>
3231_LIBCPP_NODISCARD_EXT _LIBCPP_CONSTEXPR_AFTER_CXX17 bool
3232is_partitioned(_InputIterator __first, _InputIterator __last, _Predicate __pred)
3233{
3234    for (; __first != __last; ++__first)
3235        if (!__pred(*__first))
3236            break;
3237    if ( __first == __last )
3238        return true;
3239    ++__first;
3240    for (; __first != __last; ++__first)
3241        if (__pred(*__first))
3242            return false;
3243    return true;
3244}
3245
3246// partition
3247
3248template <class _Predicate, class _ForwardIterator>
3249_ForwardIterator
3250__partition(_ForwardIterator __first, _ForwardIterator __last, _Predicate __pred, forward_iterator_tag)
3251{
3252    while (true)
3253    {
3254        if (__first == __last)
3255            return __first;
3256        if (!__pred(*__first))
3257            break;
3258        ++__first;
3259    }
3260    for (_ForwardIterator __p = __first; ++__p != __last;)
3261    {
3262        if (__pred(*__p))
3263        {
3264            swap(*__first, *__p);
3265            ++__first;
3266        }
3267    }
3268    return __first;
3269}
3270
3271template <class _Predicate, class _BidirectionalIterator>
3272_BidirectionalIterator
3273__partition(_BidirectionalIterator __first, _BidirectionalIterator __last, _Predicate __pred,
3274            bidirectional_iterator_tag)
3275{
3276    while (true)
3277    {
3278        while (true)
3279        {
3280            if (__first == __last)
3281                return __first;
3282            if (!__pred(*__first))
3283                break;
3284            ++__first;
3285        }
3286        do
3287        {
3288            if (__first == --__last)
3289                return __first;
3290        } while (!__pred(*__last));
3291        swap(*__first, *__last);
3292        ++__first;
3293    }
3294}
3295
3296template <class _ForwardIterator, class _Predicate>
3297inline _LIBCPP_INLINE_VISIBILITY
3298_ForwardIterator
3299partition(_ForwardIterator __first, _ForwardIterator __last, _Predicate __pred)
3300{
3301    return _VSTD::__partition<typename add_lvalue_reference<_Predicate>::type>
3302                            (__first, __last, __pred, typename iterator_traits<_ForwardIterator>::iterator_category());
3303}
3304
3305// partition_copy
3306
3307template <class _InputIterator, class _OutputIterator1,
3308          class _OutputIterator2, class _Predicate>
3309_LIBCPP_CONSTEXPR_AFTER_CXX17 pair<_OutputIterator1, _OutputIterator2>
3310partition_copy(_InputIterator __first, _InputIterator __last,
3311               _OutputIterator1 __out_true, _OutputIterator2 __out_false,
3312               _Predicate __pred)
3313{
3314    for (; __first != __last; ++__first)
3315    {
3316        if (__pred(*__first))
3317        {
3318            *__out_true = *__first;
3319            ++__out_true;
3320        }
3321        else
3322        {
3323            *__out_false = *__first;
3324            ++__out_false;
3325        }
3326    }
3327    return pair<_OutputIterator1, _OutputIterator2>(__out_true, __out_false);
3328}
3329
3330// partition_point
3331
3332template<class _ForwardIterator, class _Predicate>
3333_LIBCPP_CONSTEXPR_AFTER_CXX17 _ForwardIterator
3334partition_point(_ForwardIterator __first, _ForwardIterator __last, _Predicate __pred)
3335{
3336    typedef typename iterator_traits<_ForwardIterator>::difference_type difference_type;
3337    difference_type __len = _VSTD::distance(__first, __last);
3338    while (__len != 0)
3339    {
3340        difference_type __l2 = _VSTD::__half_positive(__len);
3341        _ForwardIterator __m = __first;
3342        _VSTD::advance(__m, __l2);
3343        if (__pred(*__m))
3344        {
3345            __first = ++__m;
3346            __len -= __l2 + 1;
3347        }
3348        else
3349            __len = __l2;
3350    }
3351    return __first;
3352}
3353
3354// stable_partition
3355
3356template <class _Predicate, class _ForwardIterator, class _Distance, class _Pair>
3357_ForwardIterator
3358__stable_partition(_ForwardIterator __first, _ForwardIterator __last, _Predicate __pred,
3359                   _Distance __len, _Pair __p, forward_iterator_tag __fit)
3360{
3361    // *__first is known to be false
3362    // __len >= 1
3363    if (__len == 1)
3364        return __first;
3365    if (__len == 2)
3366    {
3367        _ForwardIterator __m = __first;
3368        if (__pred(*++__m))
3369        {
3370            swap(*__first, *__m);
3371            return __m;
3372        }
3373        return __first;
3374    }
3375    if (__len <= __p.second)
3376    {   // The buffer is big enough to use
3377        typedef typename iterator_traits<_ForwardIterator>::value_type value_type;
3378        __destruct_n __d(0);
3379        unique_ptr<value_type, __destruct_n&> __h(__p.first, __d);
3380        // Move the falses into the temporary buffer, and the trues to the front of the line
3381        // Update __first to always point to the end of the trues
3382        value_type* __t = __p.first;
3383        ::new(__t) value_type(_VSTD::move(*__first));
3384        __d.__incr((value_type*)0);
3385        ++__t;
3386        _ForwardIterator __i = __first;
3387        while (++__i != __last)
3388        {
3389            if (__pred(*__i))
3390            {
3391                *__first = _VSTD::move(*__i);
3392                ++__first;
3393            }
3394            else
3395            {
3396                ::new(__t) value_type(_VSTD::move(*__i));
3397                __d.__incr((value_type*)0);
3398                ++__t;
3399            }
3400        }
3401        // All trues now at start of range, all falses in buffer
3402        // Move falses back into range, but don't mess up __first which points to first false
3403        __i = __first;
3404        for (value_type* __t2 = __p.first; __t2 < __t; ++__t2, (void) ++__i)
3405            *__i = _VSTD::move(*__t2);
3406        // __h destructs moved-from values out of the temp buffer, but doesn't deallocate buffer
3407        return __first;
3408    }
3409    // Else not enough buffer, do in place
3410    // __len >= 3
3411    _ForwardIterator __m = __first;
3412    _Distance __len2 = __len / 2;  // __len2 >= 2
3413    _VSTD::advance(__m, __len2);
3414    // recurse on [__first, __m), *__first know to be false
3415    // F?????????????????
3416    // f       m         l
3417    typedef typename add_lvalue_reference<_Predicate>::type _PredRef;
3418    _ForwardIterator __first_false = __stable_partition<_PredRef>(__first, __m, __pred, __len2, __p, __fit);
3419    // TTTFFFFF??????????
3420    // f  ff   m         l
3421    // recurse on [__m, __last], except increase __m until *(__m) is false, *__last know to be true
3422    _ForwardIterator __m1 = __m;
3423    _ForwardIterator __second_false = __last;
3424    _Distance __len_half = __len - __len2;
3425    while (__pred(*__m1))
3426    {
3427        if (++__m1 == __last)
3428            goto __second_half_done;
3429        --__len_half;
3430    }
3431    // TTTFFFFFTTTF??????
3432    // f  ff   m  m1     l
3433    __second_false = __stable_partition<_PredRef>(__m1, __last, __pred, __len_half, __p, __fit);
3434__second_half_done:
3435    // TTTFFFFFTTTTTFFFFF
3436    // f  ff   m    sf   l
3437    return _VSTD::rotate(__first_false, __m, __second_false);
3438    // TTTTTTTTFFFFFFFFFF
3439    //         |
3440}
3441
3442struct __return_temporary_buffer
3443{
3444    template <class _Tp>
3445    _LIBCPP_INLINE_VISIBILITY void operator()(_Tp* __p) const {_VSTD::return_temporary_buffer(__p);}
3446};
3447
3448template <class _Predicate, class _ForwardIterator>
3449_ForwardIterator
3450__stable_partition(_ForwardIterator __first, _ForwardIterator __last, _Predicate __pred,
3451                   forward_iterator_tag)
3452{
3453    const unsigned __alloc_limit = 3;  // might want to make this a function of trivial assignment
3454    // Either prove all true and return __first or point to first false
3455    while (true)
3456    {
3457        if (__first == __last)
3458            return __first;
3459        if (!__pred(*__first))
3460            break;
3461        ++__first;
3462    }
3463    // We now have a reduced range [__first, __last)
3464    // *__first is known to be false
3465    typedef typename iterator_traits<_ForwardIterator>::difference_type difference_type;
3466    typedef typename iterator_traits<_ForwardIterator>::value_type value_type;
3467    difference_type __len = _VSTD::distance(__first, __last);
3468    pair<value_type*, ptrdiff_t> __p(0, 0);
3469    unique_ptr<value_type, __return_temporary_buffer> __h;
3470    if (__len >= __alloc_limit)
3471    {
3472        __p = _VSTD::get_temporary_buffer<value_type>(__len);
3473        __h.reset(__p.first);
3474    }
3475    return __stable_partition<typename add_lvalue_reference<_Predicate>::type>
3476                             (__first, __last, __pred, __len, __p, forward_iterator_tag());
3477}
3478
3479template <class _Predicate, class _BidirectionalIterator, class _Distance, class _Pair>
3480_BidirectionalIterator
3481__stable_partition(_BidirectionalIterator __first, _BidirectionalIterator __last, _Predicate __pred,
3482                   _Distance __len, _Pair __p, bidirectional_iterator_tag __bit)
3483{
3484    // *__first is known to be false
3485    // *__last is known to be true
3486    // __len >= 2
3487    if (__len == 2)
3488    {
3489        swap(*__first, *__last);
3490        return __last;
3491    }
3492    if (__len == 3)
3493    {
3494        _BidirectionalIterator __m = __first;
3495        if (__pred(*++__m))
3496        {
3497            swap(*__first, *__m);
3498            swap(*__m, *__last);
3499            return __last;
3500        }
3501        swap(*__m, *__last);
3502        swap(*__first, *__m);
3503        return __m;
3504    }
3505    if (__len <= __p.second)
3506    {   // The buffer is big enough to use
3507        typedef typename iterator_traits<_BidirectionalIterator>::value_type value_type;
3508        __destruct_n __d(0);
3509        unique_ptr<value_type, __destruct_n&> __h(__p.first, __d);
3510        // Move the falses into the temporary buffer, and the trues to the front of the line
3511        // Update __first to always point to the end of the trues
3512        value_type* __t = __p.first;
3513        ::new(__t) value_type(_VSTD::move(*__first));
3514        __d.__incr((value_type*)0);
3515        ++__t;
3516        _BidirectionalIterator __i = __first;
3517        while (++__i != __last)
3518        {
3519            if (__pred(*__i))
3520            {
3521                *__first = _VSTD::move(*__i);
3522                ++__first;
3523            }
3524            else
3525            {
3526                ::new(__t) value_type(_VSTD::move(*__i));
3527                __d.__incr((value_type*)0);
3528                ++__t;
3529            }
3530        }
3531        // move *__last, known to be true
3532        *__first = _VSTD::move(*__i);
3533        __i = ++__first;
3534        // All trues now at start of range, all falses in buffer
3535        // Move falses back into range, but don't mess up __first which points to first false
3536        for (value_type* __t2 = __p.first; __t2 < __t; ++__t2, (void) ++__i)
3537            *__i = _VSTD::move(*__t2);
3538        // __h destructs moved-from values out of the temp buffer, but doesn't deallocate buffer
3539        return __first;
3540    }
3541    // Else not enough buffer, do in place
3542    // __len >= 4
3543    _BidirectionalIterator __m = __first;
3544    _Distance __len2 = __len / 2;  // __len2 >= 2
3545    _VSTD::advance(__m, __len2);
3546    // recurse on [__first, __m-1], except reduce __m-1 until *(__m-1) is true, *__first know to be false
3547    // F????????????????T
3548    // f       m        l
3549    _BidirectionalIterator __m1 = __m;
3550    _BidirectionalIterator __first_false = __first;
3551    _Distance __len_half = __len2;
3552    while (!__pred(*--__m1))
3553    {
3554        if (__m1 == __first)
3555            goto __first_half_done;
3556        --__len_half;
3557    }
3558    // F???TFFF?????????T
3559    // f   m1  m        l
3560    typedef typename add_lvalue_reference<_Predicate>::type _PredRef;
3561    __first_false = __stable_partition<_PredRef>(__first, __m1, __pred, __len_half, __p, __bit);
3562__first_half_done:
3563    // TTTFFFFF?????????T
3564    // f  ff   m        l
3565    // recurse on [__m, __last], except increase __m until *(__m) is false, *__last know to be true
3566    __m1 = __m;
3567    _BidirectionalIterator __second_false = __last;
3568    ++__second_false;
3569    __len_half = __len - __len2;
3570    while (__pred(*__m1))
3571    {
3572        if (++__m1 == __last)
3573            goto __second_half_done;
3574        --__len_half;
3575    }
3576    // TTTFFFFFTTTF?????T
3577    // f  ff   m  m1    l
3578    __second_false = __stable_partition<_PredRef>(__m1, __last, __pred, __len_half, __p, __bit);
3579__second_half_done:
3580    // TTTFFFFFTTTTTFFFFF
3581    // f  ff   m    sf  l
3582    return _VSTD::rotate(__first_false, __m, __second_false);
3583    // TTTTTTTTFFFFFFFFFF
3584    //         |
3585}
3586
3587template <class _Predicate, class _BidirectionalIterator>
3588_BidirectionalIterator
3589__stable_partition(_BidirectionalIterator __first, _BidirectionalIterator __last, _Predicate __pred,
3590                   bidirectional_iterator_tag)
3591{
3592    typedef typename iterator_traits<_BidirectionalIterator>::difference_type difference_type;
3593    typedef typename iterator_traits<_BidirectionalIterator>::value_type value_type;
3594    const difference_type __alloc_limit = 4;  // might want to make this a function of trivial assignment
3595    // Either prove all true and return __first or point to first false
3596    while (true)
3597    {
3598        if (__first == __last)
3599            return __first;
3600        if (!__pred(*__first))
3601            break;
3602        ++__first;
3603    }
3604    // __first points to first false, everything prior to __first is already set.
3605    // Either prove [__first, __last) is all false and return __first, or point __last to last true
3606    do
3607    {
3608        if (__first == --__last)
3609            return __first;
3610    } while (!__pred(*__last));
3611    // We now have a reduced range [__first, __last]
3612    // *__first is known to be false
3613    // *__last is known to be true
3614    // __len >= 2
3615    difference_type __len = _VSTD::distance(__first, __last) + 1;
3616    pair<value_type*, ptrdiff_t> __p(0, 0);
3617    unique_ptr<value_type, __return_temporary_buffer> __h;
3618    if (__len >= __alloc_limit)
3619    {
3620        __p = _VSTD::get_temporary_buffer<value_type>(__len);
3621        __h.reset(__p.first);
3622    }
3623    return __stable_partition<typename add_lvalue_reference<_Predicate>::type>
3624                             (__first, __last, __pred, __len, __p, bidirectional_iterator_tag());
3625}
3626
3627template <class _ForwardIterator, class _Predicate>
3628inline _LIBCPP_INLINE_VISIBILITY
3629_ForwardIterator
3630stable_partition(_ForwardIterator __first, _ForwardIterator __last, _Predicate __pred)
3631{
3632    return __stable_partition<typename add_lvalue_reference<_Predicate>::type>
3633                             (__first, __last, __pred, typename iterator_traits<_ForwardIterator>::iterator_category());
3634}
3635
3636// is_sorted_until
3637
3638template <class _ForwardIterator, class _Compare>
3639_LIBCPP_NODISCARD_EXT _LIBCPP_CONSTEXPR_AFTER_CXX17 _ForwardIterator
3640is_sorted_until(_ForwardIterator __first, _ForwardIterator __last, _Compare __comp)
3641{
3642    if (__first != __last)
3643    {
3644        _ForwardIterator __i = __first;
3645        while (++__i != __last)
3646        {
3647            if (__comp(*__i, *__first))
3648                return __i;
3649            __first = __i;
3650        }
3651    }
3652    return __last;
3653}
3654
3655template<class _ForwardIterator>
3656_LIBCPP_NODISCARD_EXT inline
3657_LIBCPP_INLINE_VISIBILITY _LIBCPP_CONSTEXPR_AFTER_CXX17
3658_ForwardIterator
3659is_sorted_until(_ForwardIterator __first, _ForwardIterator __last)
3660{
3661    return _VSTD::is_sorted_until(__first, __last, __less<typename iterator_traits<_ForwardIterator>::value_type>());
3662}
3663
3664// is_sorted
3665
3666template <class _ForwardIterator, class _Compare>
3667_LIBCPP_NODISCARD_EXT inline
3668_LIBCPP_INLINE_VISIBILITY _LIBCPP_CONSTEXPR_AFTER_CXX17
3669bool
3670is_sorted(_ForwardIterator __first, _ForwardIterator __last, _Compare __comp)
3671{
3672    return _VSTD::is_sorted_until(__first, __last, __comp) == __last;
3673}
3674
3675template<class _ForwardIterator>
3676_LIBCPP_NODISCARD_EXT inline
3677_LIBCPP_INLINE_VISIBILITY _LIBCPP_CONSTEXPR_AFTER_CXX17
3678bool
3679is_sorted(_ForwardIterator __first, _ForwardIterator __last)
3680{
3681    return _VSTD::is_sorted(__first, __last, __less<typename iterator_traits<_ForwardIterator>::value_type>());
3682}
3683
3684// sort
3685
3686// stable, 2-3 compares, 0-2 swaps
3687
3688template <class _Compare, class _ForwardIterator>
3689unsigned
3690__sort3(_ForwardIterator __x, _ForwardIterator __y, _ForwardIterator __z, _Compare __c)
3691{
3692    unsigned __r = 0;
3693    if (!__c(*__y, *__x))          // if x <= y
3694    {
3695        if (!__c(*__z, *__y))      // if y <= z
3696            return __r;            // x <= y && y <= z
3697                                   // x <= y && y > z
3698        swap(*__y, *__z);          // x <= z && y < z
3699        __r = 1;
3700        if (__c(*__y, *__x))       // if x > y
3701        {
3702            swap(*__x, *__y);      // x < y && y <= z
3703            __r = 2;
3704        }
3705        return __r;                // x <= y && y < z
3706    }
3707    if (__c(*__z, *__y))           // x > y, if y > z
3708    {
3709        swap(*__x, *__z);          // x < y && y < z
3710        __r = 1;
3711        return __r;
3712    }
3713    swap(*__x, *__y);              // x > y && y <= z
3714    __r = 1;                       // x < y && x <= z
3715    if (__c(*__z, *__y))           // if y > z
3716    {
3717        swap(*__y, *__z);          // x <= y && y < z
3718        __r = 2;
3719    }
3720    return __r;
3721}                                  // x <= y && y <= z
3722
3723// stable, 3-6 compares, 0-5 swaps
3724
3725template <class _Compare, class _ForwardIterator>
3726unsigned
3727__sort4(_ForwardIterator __x1, _ForwardIterator __x2, _ForwardIterator __x3,
3728            _ForwardIterator __x4, _Compare __c)
3729{
3730    unsigned __r = __sort3<_Compare>(__x1, __x2, __x3, __c);
3731    if (__c(*__x4, *__x3))
3732    {
3733        swap(*__x3, *__x4);
3734        ++__r;
3735        if (__c(*__x3, *__x2))
3736        {
3737            swap(*__x2, *__x3);
3738            ++__r;
3739            if (__c(*__x2, *__x1))
3740            {
3741                swap(*__x1, *__x2);
3742                ++__r;
3743            }
3744        }
3745    }
3746    return __r;
3747}
3748
3749// stable, 4-10 compares, 0-9 swaps
3750
3751template <class _Compare, class _ForwardIterator>
3752_LIBCPP_HIDDEN
3753unsigned
3754__sort5(_ForwardIterator __x1, _ForwardIterator __x2, _ForwardIterator __x3,
3755            _ForwardIterator __x4, _ForwardIterator __x5, _Compare __c)
3756{
3757    unsigned __r = __sort4<_Compare>(__x1, __x2, __x3, __x4, __c);
3758    if (__c(*__x5, *__x4))
3759    {
3760        swap(*__x4, *__x5);
3761        ++__r;
3762        if (__c(*__x4, *__x3))
3763        {
3764            swap(*__x3, *__x4);
3765            ++__r;
3766            if (__c(*__x3, *__x2))
3767            {
3768                swap(*__x2, *__x3);
3769                ++__r;
3770                if (__c(*__x2, *__x1))
3771                {
3772                    swap(*__x1, *__x2);
3773                    ++__r;
3774                }
3775            }
3776        }
3777    }
3778    return __r;
3779}
3780
3781// Assumes size > 0
3782template <class _Compare, class _BirdirectionalIterator>
3783void
3784__selection_sort(_BirdirectionalIterator __first, _BirdirectionalIterator __last, _Compare __comp)
3785{
3786    _BirdirectionalIterator __lm1 = __last;
3787    for (--__lm1; __first != __lm1; ++__first)
3788    {
3789        _BirdirectionalIterator __i = _VSTD::min_element<_BirdirectionalIterator,
3790                                                        typename add_lvalue_reference<_Compare>::type>
3791                                                       (__first, __last, __comp);
3792        if (__i != __first)
3793            swap(*__first, *__i);
3794    }
3795}
3796
3797template <class _Compare, class _BirdirectionalIterator>
3798void
3799__insertion_sort(_BirdirectionalIterator __first, _BirdirectionalIterator __last, _Compare __comp)
3800{
3801    typedef typename iterator_traits<_BirdirectionalIterator>::value_type value_type;
3802    if (__first != __last)
3803    {
3804        _BirdirectionalIterator __i = __first;
3805        for (++__i; __i != __last; ++__i)
3806        {
3807            _BirdirectionalIterator __j = __i;
3808            value_type __t(_VSTD::move(*__j));
3809            for (_BirdirectionalIterator __k = __i; __k != __first && __comp(__t,  *--__k); --__j)
3810                *__j = _VSTD::move(*__k);
3811            *__j = _VSTD::move(__t);
3812        }
3813    }
3814}
3815
3816template <class _Compare, class _RandomAccessIterator>
3817void
3818__insertion_sort_3(_RandomAccessIterator __first, _RandomAccessIterator __last, _Compare __comp)
3819{
3820    typedef typename iterator_traits<_RandomAccessIterator>::value_type value_type;
3821    _RandomAccessIterator __j = __first+2;
3822    __sort3<_Compare>(__first, __first+1, __j, __comp);
3823    for (_RandomAccessIterator __i = __j+1; __i != __last; ++__i)
3824    {
3825        if (__comp(*__i, *__j))
3826        {
3827            value_type __t(_VSTD::move(*__i));
3828            _RandomAccessIterator __k = __j;
3829            __j = __i;
3830            do
3831            {
3832                *__j = _VSTD::move(*__k);
3833                __j = __k;
3834            } while (__j != __first && __comp(__t, *--__k));
3835            *__j = _VSTD::move(__t);
3836        }
3837        __j = __i;
3838    }
3839}
3840
3841template <class _Compare, class _RandomAccessIterator>
3842bool
3843__insertion_sort_incomplete(_RandomAccessIterator __first, _RandomAccessIterator __last, _Compare __comp)
3844{
3845    switch (__last - __first)
3846    {
3847    case 0:
3848    case 1:
3849        return true;
3850    case 2:
3851        if (__comp(*--__last, *__first))
3852            swap(*__first, *__last);
3853        return true;
3854    case 3:
3855        _VSTD::__sort3<_Compare>(__first, __first+1, --__last, __comp);
3856        return true;
3857    case 4:
3858        _VSTD::__sort4<_Compare>(__first, __first+1, __first+2, --__last, __comp);
3859        return true;
3860    case 5:
3861        _VSTD::__sort5<_Compare>(__first, __first+1, __first+2, __first+3, --__last, __comp);
3862        return true;
3863    }
3864    typedef typename iterator_traits<_RandomAccessIterator>::value_type value_type;
3865    _RandomAccessIterator __j = __first+2;
3866    __sort3<_Compare>(__first, __first+1, __j, __comp);
3867    const unsigned __limit = 8;
3868    unsigned __count = 0;
3869    for (_RandomAccessIterator __i = __j+1; __i != __last; ++__i)
3870    {
3871        if (__comp(*__i, *__j))
3872        {
3873            value_type __t(_VSTD::move(*__i));
3874            _RandomAccessIterator __k = __j;
3875            __j = __i;
3876            do
3877            {
3878                *__j = _VSTD::move(*__k);
3879                __j = __k;
3880            } while (__j != __first && __comp(__t, *--__k));
3881            *__j = _VSTD::move(__t);
3882            if (++__count == __limit)
3883                return ++__i == __last;
3884        }
3885        __j = __i;
3886    }
3887    return true;
3888}
3889
3890template <class _Compare, class _BirdirectionalIterator>
3891void
3892__insertion_sort_move(_BirdirectionalIterator __first1, _BirdirectionalIterator __last1,
3893                      typename iterator_traits<_BirdirectionalIterator>::value_type* __first2, _Compare __comp)
3894{
3895    typedef typename iterator_traits<_BirdirectionalIterator>::value_type value_type;
3896    if (__first1 != __last1)
3897    {
3898        __destruct_n __d(0);
3899        unique_ptr<value_type, __destruct_n&> __h(__first2, __d);
3900        value_type* __last2 = __first2;
3901        ::new(__last2) value_type(_VSTD::move(*__first1));
3902        __d.__incr((value_type*)0);
3903        for (++__last2; ++__first1 != __last1; ++__last2)
3904        {
3905            value_type* __j2 = __last2;
3906            value_type* __i2 = __j2;
3907            if (__comp(*__first1, *--__i2))
3908            {
3909                ::new(__j2) value_type(_VSTD::move(*__i2));
3910                __d.__incr((value_type*)0);
3911                for (--__j2; __i2 != __first2 && __comp(*__first1,  *--__i2); --__j2)
3912                    *__j2 = _VSTD::move(*__i2);
3913                *__j2 = _VSTD::move(*__first1);
3914            }
3915            else
3916            {
3917                ::new(__j2) value_type(_VSTD::move(*__first1));
3918                __d.__incr((value_type*)0);
3919            }
3920        }
3921        __h.release();
3922    }
3923}
3924
3925template <class _Compare, class _RandomAccessIterator>
3926void
3927__sort(_RandomAccessIterator __first, _RandomAccessIterator __last, _Compare __comp)
3928{
3929    // _Compare is known to be a reference type
3930    typedef typename iterator_traits<_RandomAccessIterator>::difference_type difference_type;
3931    typedef typename iterator_traits<_RandomAccessIterator>::value_type value_type;
3932    const difference_type __limit = is_trivially_copy_constructible<value_type>::value &&
3933                                    is_trivially_copy_assignable<value_type>::value ? 30 : 6;
3934    while (true)
3935    {
3936    __restart:
3937        difference_type __len = __last - __first;
3938        switch (__len)
3939        {
3940        case 0:
3941        case 1:
3942            return;
3943        case 2:
3944            if (__comp(*--__last, *__first))
3945                swap(*__first, *__last);
3946            return;
3947        case 3:
3948            _VSTD::__sort3<_Compare>(__first, __first+1, --__last, __comp);
3949            return;
3950        case 4:
3951            _VSTD::__sort4<_Compare>(__first, __first+1, __first+2, --__last, __comp);
3952            return;
3953        case 5:
3954            _VSTD::__sort5<_Compare>(__first, __first+1, __first+2, __first+3, --__last, __comp);
3955            return;
3956        }
3957        if (__len <= __limit)
3958        {
3959            _VSTD::__insertion_sort_3<_Compare>(__first, __last, __comp);
3960            return;
3961        }
3962        // __len > 5
3963        _RandomAccessIterator __m = __first;
3964        _RandomAccessIterator __lm1 = __last;
3965        --__lm1;
3966        unsigned __n_swaps;
3967        {
3968        difference_type __delta;
3969        if (__len >= 1000)
3970        {
3971            __delta = __len/2;
3972            __m += __delta;
3973            __delta /= 2;
3974            __n_swaps = _VSTD::__sort5<_Compare>(__first, __first + __delta, __m, __m+__delta, __lm1, __comp);
3975        }
3976        else
3977        {
3978            __delta = __len/2;
3979            __m += __delta;
3980            __n_swaps = _VSTD::__sort3<_Compare>(__first, __m, __lm1, __comp);
3981        }
3982        }
3983        // *__m is median
3984        // partition [__first, __m) < *__m and *__m <= [__m, __last)
3985        // (this inhibits tossing elements equivalent to __m around unnecessarily)
3986        _RandomAccessIterator __i = __first;
3987        _RandomAccessIterator __j = __lm1;
3988        // j points beyond range to be tested, *__m is known to be <= *__lm1
3989        // The search going up is known to be guarded but the search coming down isn't.
3990        // Prime the downward search with a guard.
3991        if (!__comp(*__i, *__m))  // if *__first == *__m
3992        {
3993            // *__first == *__m, *__first doesn't go in first part
3994            // manually guard downward moving __j against __i
3995            while (true)
3996            {
3997                if (__i == --__j)
3998                {
3999                    // *__first == *__m, *__m <= all other elements
4000                    // Parition instead into [__first, __i) == *__first and *__first < [__i, __last)
4001                    ++__i;  // __first + 1
4002                    __j = __last;
4003                    if (!__comp(*__first, *--__j))  // we need a guard if *__first == *(__last-1)
4004                    {
4005                        while (true)
4006                        {
4007                            if (__i == __j)
4008                                return;  // [__first, __last) all equivalent elements
4009                            if (__comp(*__first, *__i))
4010                            {
4011                                swap(*__i, *__j);
4012                                ++__n_swaps;
4013                                ++__i;
4014                                break;
4015                            }
4016                            ++__i;
4017                        }
4018                    }
4019                    // [__first, __i) == *__first and *__first < [__j, __last) and __j == __last - 1
4020                    if (__i == __j)
4021                        return;
4022                    while (true)
4023                    {
4024                        while (!__comp(*__first, *__i))
4025                            ++__i;
4026                        while (__comp(*__first, *--__j))
4027                            ;
4028                        if (__i >= __j)
4029                            break;
4030                        swap(*__i, *__j);
4031                        ++__n_swaps;
4032                        ++__i;
4033                    }
4034                    // [__first, __i) == *__first and *__first < [__i, __last)
4035                    // The first part is sorted, sort the secod part
4036                    // _VSTD::__sort<_Compare>(__i, __last, __comp);
4037                    __first = __i;
4038                    goto __restart;
4039                }
4040                if (__comp(*__j, *__m))
4041                {
4042                    swap(*__i, *__j);
4043                    ++__n_swaps;
4044                    break;  // found guard for downward moving __j, now use unguarded partition
4045                }
4046            }
4047        }
4048        // It is known that *__i < *__m
4049        ++__i;
4050        // j points beyond range to be tested, *__m is known to be <= *__lm1
4051        // if not yet partitioned...
4052        if (__i < __j)
4053        {
4054            // known that *(__i - 1) < *__m
4055            // known that __i <= __m
4056            while (true)
4057            {
4058                // __m still guards upward moving __i
4059                while (__comp(*__i, *__m))
4060                    ++__i;
4061                // It is now known that a guard exists for downward moving __j
4062                while (!__comp(*--__j, *__m))
4063                    ;
4064                if (__i > __j)
4065                    break;
4066                swap(*__i, *__j);
4067                ++__n_swaps;
4068                // It is known that __m != __j
4069                // If __m just moved, follow it
4070                if (__m == __i)
4071                    __m = __j;
4072                ++__i;
4073            }
4074        }
4075        // [__first, __i) < *__m and *__m <= [__i, __last)
4076        if (__i != __m && __comp(*__m, *__i))
4077        {
4078            swap(*__i, *__m);
4079            ++__n_swaps;
4080        }
4081        // [__first, __i) < *__i and *__i <= [__i+1, __last)
4082        // If we were given a perfect partition, see if insertion sort is quick...
4083        if (__n_swaps == 0)
4084        {
4085            bool __fs = _VSTD::__insertion_sort_incomplete<_Compare>(__first, __i, __comp);
4086            if (_VSTD::__insertion_sort_incomplete<_Compare>(__i+1, __last, __comp))
4087            {
4088                if (__fs)
4089                    return;
4090                __last = __i;
4091                continue;
4092            }
4093            else
4094            {
4095                if (__fs)
4096                {
4097                    __first = ++__i;
4098                    continue;
4099                }
4100            }
4101        }
4102        // sort smaller range with recursive call and larger with tail recursion elimination
4103        if (__i - __first < __last - __i)
4104        {
4105            _VSTD::__sort<_Compare>(__first, __i, __comp);
4106            // _VSTD::__sort<_Compare>(__i+1, __last, __comp);
4107            __first = ++__i;
4108        }
4109        else
4110        {
4111            _VSTD::__sort<_Compare>(__i+1, __last, __comp);
4112            // _VSTD::__sort<_Compare>(__first, __i, __comp);
4113            __last = __i;
4114        }
4115    }
4116}
4117
4118// This forwarder keeps the top call and the recursive calls using the same instantiation, forcing a reference _Compare
4119template <class _RandomAccessIterator, class _Compare>
4120inline _LIBCPP_INLINE_VISIBILITY
4121void
4122sort(_RandomAccessIterator __first, _RandomAccessIterator __last, _Compare __comp)
4123{
4124    typedef typename __comp_ref_type<_Compare>::type _Comp_ref;
4125    _VSTD::__sort<_Comp_ref>(__first, __last, _Comp_ref(__comp));
4126}
4127
4128template <class _RandomAccessIterator>
4129inline _LIBCPP_INLINE_VISIBILITY
4130void
4131sort(_RandomAccessIterator __first, _RandomAccessIterator __last)
4132{
4133    _VSTD::sort(__first, __last, __less<typename iterator_traits<_RandomAccessIterator>::value_type>());
4134}
4135
4136template <class _Tp>
4137inline _LIBCPP_INLINE_VISIBILITY
4138void
4139sort(_Tp** __first, _Tp** __last)
4140{
4141    _VSTD::sort((size_t*)__first, (size_t*)__last, __less<size_t>());
4142}
4143
4144template <class _Tp>
4145inline _LIBCPP_INLINE_VISIBILITY
4146void
4147sort(__wrap_iter<_Tp*> __first, __wrap_iter<_Tp*> __last)
4148{
4149    _VSTD::sort(__first.base(), __last.base());
4150}
4151
4152template <class _Tp, class _Compare>
4153inline _LIBCPP_INLINE_VISIBILITY
4154void
4155sort(__wrap_iter<_Tp*> __first, __wrap_iter<_Tp*> __last, _Compare __comp)
4156{
4157    typedef typename add_lvalue_reference<_Compare>::type _Comp_ref;
4158    _VSTD::sort<_Tp*, _Comp_ref>(__first.base(), __last.base(), __comp);
4159}
4160
4161_LIBCPP_EXTERN_TEMPLATE(_LIBCPP_FUNC_VIS void __sort<__less<char>&, char*>(char*, char*, __less<char>&))
4162_LIBCPP_EXTERN_TEMPLATE(_LIBCPP_FUNC_VIS void __sort<__less<wchar_t>&, wchar_t*>(wchar_t*, wchar_t*, __less<wchar_t>&))
4163_LIBCPP_EXTERN_TEMPLATE(_LIBCPP_FUNC_VIS void __sort<__less<signed char>&, signed char*>(signed char*, signed char*, __less<signed char>&))
4164_LIBCPP_EXTERN_TEMPLATE(_LIBCPP_FUNC_VIS void __sort<__less<unsigned char>&, unsigned char*>(unsigned char*, unsigned char*, __less<unsigned char>&))
4165_LIBCPP_EXTERN_TEMPLATE(_LIBCPP_FUNC_VIS void __sort<__less<short>&, short*>(short*, short*, __less<short>&))
4166_LIBCPP_EXTERN_TEMPLATE(_LIBCPP_FUNC_VIS void __sort<__less<unsigned short>&, unsigned short*>(unsigned short*, unsigned short*, __less<unsigned short>&))
4167_LIBCPP_EXTERN_TEMPLATE(_LIBCPP_FUNC_VIS void __sort<__less<int>&, int*>(int*, int*, __less<int>&))
4168_LIBCPP_EXTERN_TEMPLATE(_LIBCPP_FUNC_VIS void __sort<__less<unsigned>&, unsigned*>(unsigned*, unsigned*, __less<unsigned>&))
4169_LIBCPP_EXTERN_TEMPLATE(_LIBCPP_FUNC_VIS void __sort<__less<long>&, long*>(long*, long*, __less<long>&))
4170_LIBCPP_EXTERN_TEMPLATE(_LIBCPP_FUNC_VIS void __sort<__less<unsigned long>&, unsigned long*>(unsigned long*, unsigned long*, __less<unsigned long>&))
4171_LIBCPP_EXTERN_TEMPLATE(_LIBCPP_FUNC_VIS void __sort<__less<long long>&, long long*>(long long*, long long*, __less<long long>&))
4172_LIBCPP_EXTERN_TEMPLATE(_LIBCPP_FUNC_VIS void __sort<__less<unsigned long long>&, unsigned long long*>(unsigned long long*, unsigned long long*, __less<unsigned long long>&))
4173_LIBCPP_EXTERN_TEMPLATE(_LIBCPP_FUNC_VIS void __sort<__less<float>&, float*>(float*, float*, __less<float>&))
4174_LIBCPP_EXTERN_TEMPLATE(_LIBCPP_FUNC_VIS void __sort<__less<double>&, double*>(double*, double*, __less<double>&))
4175_LIBCPP_EXTERN_TEMPLATE(_LIBCPP_FUNC_VIS void __sort<__less<long double>&, long double*>(long double*, long double*, __less<long double>&))
4176
4177_LIBCPP_EXTERN_TEMPLATE(_LIBCPP_FUNC_VIS bool __insertion_sort_incomplete<__less<char>&, char*>(char*, char*, __less<char>&))
4178_LIBCPP_EXTERN_TEMPLATE(_LIBCPP_FUNC_VIS bool __insertion_sort_incomplete<__less<wchar_t>&, wchar_t*>(wchar_t*, wchar_t*, __less<wchar_t>&))
4179_LIBCPP_EXTERN_TEMPLATE(_LIBCPP_FUNC_VIS bool __insertion_sort_incomplete<__less<signed char>&, signed char*>(signed char*, signed char*, __less<signed char>&))
4180_LIBCPP_EXTERN_TEMPLATE(_LIBCPP_FUNC_VIS bool __insertion_sort_incomplete<__less<unsigned char>&, unsigned char*>(unsigned char*, unsigned char*, __less<unsigned char>&))
4181_LIBCPP_EXTERN_TEMPLATE(_LIBCPP_FUNC_VIS bool __insertion_sort_incomplete<__less<short>&, short*>(short*, short*, __less<short>&))
4182_LIBCPP_EXTERN_TEMPLATE(_LIBCPP_FUNC_VIS bool __insertion_sort_incomplete<__less<unsigned short>&, unsigned short*>(unsigned short*, unsigned short*, __less<unsigned short>&))
4183_LIBCPP_EXTERN_TEMPLATE(_LIBCPP_FUNC_VIS bool __insertion_sort_incomplete<__less<int>&, int*>(int*, int*, __less<int>&))
4184_LIBCPP_EXTERN_TEMPLATE(_LIBCPP_FUNC_VIS bool __insertion_sort_incomplete<__less<unsigned>&, unsigned*>(unsigned*, unsigned*, __less<unsigned>&))
4185_LIBCPP_EXTERN_TEMPLATE(_LIBCPP_FUNC_VIS bool __insertion_sort_incomplete<__less<long>&, long*>(long*, long*, __less<long>&))
4186_LIBCPP_EXTERN_TEMPLATE(_LIBCPP_FUNC_VIS bool __insertion_sort_incomplete<__less<unsigned long>&, unsigned long*>(unsigned long*, unsigned long*, __less<unsigned long>&))
4187_LIBCPP_EXTERN_TEMPLATE(_LIBCPP_FUNC_VIS bool __insertion_sort_incomplete<__less<long long>&, long long*>(long long*, long long*, __less<long long>&))
4188_LIBCPP_EXTERN_TEMPLATE(_LIBCPP_FUNC_VIS bool __insertion_sort_incomplete<__less<unsigned long long>&, unsigned long long*>(unsigned long long*, unsigned long long*, __less<unsigned long long>&))
4189_LIBCPP_EXTERN_TEMPLATE(_LIBCPP_FUNC_VIS bool __insertion_sort_incomplete<__less<float>&, float*>(float*, float*, __less<float>&))
4190_LIBCPP_EXTERN_TEMPLATE(_LIBCPP_FUNC_VIS bool __insertion_sort_incomplete<__less<double>&, double*>(double*, double*, __less<double>&))
4191_LIBCPP_EXTERN_TEMPLATE(_LIBCPP_FUNC_VIS bool __insertion_sort_incomplete<__less<long double>&, long double*>(long double*, long double*, __less<long double>&))
4192
4193_LIBCPP_EXTERN_TEMPLATE(_LIBCPP_FUNC_VIS unsigned __sort5<__less<long double>&, long double*>(long double*, long double*, long double*, long double*, long double*, __less<long double>&))
4194
4195// lower_bound
4196
4197template <class _Compare, class _ForwardIterator, class _Tp>
4198_LIBCPP_CONSTEXPR_AFTER_CXX17 _ForwardIterator
4199__lower_bound(_ForwardIterator __first, _ForwardIterator __last, const _Tp& __value_, _Compare __comp)
4200{
4201    typedef typename iterator_traits<_ForwardIterator>::difference_type difference_type;
4202    difference_type __len = _VSTD::distance(__first, __last);
4203    while (__len != 0)
4204    {
4205        difference_type __l2 = _VSTD::__half_positive(__len);
4206        _ForwardIterator __m = __first;
4207        _VSTD::advance(__m, __l2);
4208        if (__comp(*__m, __value_))
4209        {
4210            __first = ++__m;
4211            __len -= __l2 + 1;
4212        }
4213        else
4214            __len = __l2;
4215    }
4216    return __first;
4217}
4218
4219template <class _ForwardIterator, class _Tp, class _Compare>
4220_LIBCPP_NODISCARD_EXT inline
4221_LIBCPP_INLINE_VISIBILITY _LIBCPP_CONSTEXPR_AFTER_CXX17
4222_ForwardIterator
4223lower_bound(_ForwardIterator __first, _ForwardIterator __last, const _Tp& __value_, _Compare __comp)
4224{
4225    typedef typename add_lvalue_reference<_Compare>::type _Comp_ref;
4226    return __lower_bound<_Comp_ref>(__first, __last, __value_, __comp);
4227}
4228
4229template <class _ForwardIterator, class _Tp>
4230_LIBCPP_NODISCARD_EXT inline
4231_LIBCPP_INLINE_VISIBILITY _LIBCPP_CONSTEXPR_AFTER_CXX17
4232_ForwardIterator
4233lower_bound(_ForwardIterator __first, _ForwardIterator __last, const _Tp& __value_)
4234{
4235    return _VSTD::lower_bound(__first, __last, __value_,
4236                             __less<typename iterator_traits<_ForwardIterator>::value_type, _Tp>());
4237}
4238
4239// upper_bound
4240
4241template <class _Compare, class _ForwardIterator, class _Tp>
4242_LIBCPP_CONSTEXPR_AFTER_CXX17 _ForwardIterator
4243__upper_bound(_ForwardIterator __first, _ForwardIterator __last, const _Tp& __value_, _Compare __comp)
4244{
4245    typedef typename iterator_traits<_ForwardIterator>::difference_type difference_type;
4246    difference_type __len = _VSTD::distance(__first, __last);
4247    while (__len != 0)
4248    {
4249        difference_type __l2 = _VSTD::__half_positive(__len);
4250        _ForwardIterator __m = __first;
4251        _VSTD::advance(__m, __l2);
4252        if (__comp(__value_, *__m))
4253            __len = __l2;
4254        else
4255        {
4256            __first = ++__m;
4257            __len -= __l2 + 1;
4258        }
4259    }
4260    return __first;
4261}
4262
4263template <class _ForwardIterator, class _Tp, class _Compare>
4264_LIBCPP_NODISCARD_EXT inline
4265_LIBCPP_INLINE_VISIBILITY _LIBCPP_CONSTEXPR_AFTER_CXX17
4266_ForwardIterator
4267upper_bound(_ForwardIterator __first, _ForwardIterator __last, const _Tp& __value_, _Compare __comp)
4268{
4269    typedef typename add_lvalue_reference<_Compare>::type _Comp_ref;
4270    return __upper_bound<_Comp_ref>(__first, __last, __value_, __comp);
4271}
4272
4273template <class _ForwardIterator, class _Tp>
4274_LIBCPP_NODISCARD_EXT inline
4275_LIBCPP_INLINE_VISIBILITY _LIBCPP_CONSTEXPR_AFTER_CXX17
4276_ForwardIterator
4277upper_bound(_ForwardIterator __first, _ForwardIterator __last, const _Tp& __value_)
4278{
4279    return _VSTD::upper_bound(__first, __last, __value_,
4280                             __less<_Tp, typename iterator_traits<_ForwardIterator>::value_type>());
4281}
4282
4283// equal_range
4284
4285template <class _Compare, class _ForwardIterator, class _Tp>
4286_LIBCPP_CONSTEXPR_AFTER_CXX17 pair<_ForwardIterator, _ForwardIterator>
4287__equal_range(_ForwardIterator __first, _ForwardIterator __last, const _Tp& __value_, _Compare __comp)
4288{
4289    typedef typename iterator_traits<_ForwardIterator>::difference_type difference_type;
4290    difference_type __len = _VSTD::distance(__first, __last);
4291    while (__len != 0)
4292    {
4293        difference_type __l2 = _VSTD::__half_positive(__len);
4294        _ForwardIterator __m = __first;
4295        _VSTD::advance(__m, __l2);
4296        if (__comp(*__m, __value_))
4297        {
4298            __first = ++__m;
4299            __len -= __l2 + 1;
4300        }
4301        else if (__comp(__value_, *__m))
4302        {
4303            __last = __m;
4304            __len = __l2;
4305        }
4306        else
4307        {
4308            _ForwardIterator __mp1 = __m;
4309            return pair<_ForwardIterator, _ForwardIterator>
4310                   (
4311                      __lower_bound<_Compare>(__first, __m, __value_, __comp),
4312                      __upper_bound<_Compare>(++__mp1, __last, __value_, __comp)
4313                   );
4314        }
4315    }
4316    return pair<_ForwardIterator, _ForwardIterator>(__first, __first);
4317}
4318
4319template <class _ForwardIterator, class _Tp, class _Compare>
4320_LIBCPP_NODISCARD_EXT inline
4321_LIBCPP_INLINE_VISIBILITY _LIBCPP_CONSTEXPR_AFTER_CXX17
4322pair<_ForwardIterator, _ForwardIterator>
4323equal_range(_ForwardIterator __first, _ForwardIterator __last, const _Tp& __value_, _Compare __comp)
4324{
4325    typedef typename __comp_ref_type<_Compare>::type _Comp_ref;
4326    return __equal_range<_Comp_ref>(__first, __last, __value_, __comp);
4327}
4328
4329template <class _ForwardIterator, class _Tp>
4330_LIBCPP_NODISCARD_EXT inline
4331_LIBCPP_INLINE_VISIBILITY _LIBCPP_CONSTEXPR_AFTER_CXX17
4332pair<_ForwardIterator, _ForwardIterator>
4333equal_range(_ForwardIterator __first, _ForwardIterator __last, const _Tp& __value_)
4334{
4335    return _VSTD::equal_range(__first, __last, __value_,
4336                             __less<typename iterator_traits<_ForwardIterator>::value_type, _Tp>());
4337}
4338
4339// binary_search
4340
4341template <class _Compare, class _ForwardIterator, class _Tp>
4342inline _LIBCPP_INLINE_VISIBILITY _LIBCPP_CONSTEXPR_AFTER_CXX17
4343bool
4344__binary_search(_ForwardIterator __first, _ForwardIterator __last, const _Tp& __value_, _Compare __comp)
4345{
4346    __first = __lower_bound<_Compare>(__first, __last, __value_, __comp);
4347    return __first != __last && !__comp(__value_, *__first);
4348}
4349
4350template <class _ForwardIterator, class _Tp, class _Compare>
4351_LIBCPP_NODISCARD_EXT inline
4352_LIBCPP_INLINE_VISIBILITY _LIBCPP_CONSTEXPR_AFTER_CXX17
4353bool
4354binary_search(_ForwardIterator __first, _ForwardIterator __last, const _Tp& __value_, _Compare __comp)
4355{
4356    typedef typename __comp_ref_type<_Compare>::type _Comp_ref;
4357    return __binary_search<_Comp_ref>(__first, __last, __value_, __comp);
4358}
4359
4360template <class _ForwardIterator, class _Tp>
4361_LIBCPP_NODISCARD_EXT inline
4362_LIBCPP_INLINE_VISIBILITY _LIBCPP_CONSTEXPR_AFTER_CXX17
4363bool
4364binary_search(_ForwardIterator __first, _ForwardIterator __last, const _Tp& __value_)
4365{
4366    return _VSTD::binary_search(__first, __last, __value_,
4367                             __less<typename iterator_traits<_ForwardIterator>::value_type, _Tp>());
4368}
4369
4370// merge
4371
4372template <class _Compare, class _InputIterator1, class _InputIterator2, class _OutputIterator>
4373_OutputIterator
4374__merge(_InputIterator1 __first1, _InputIterator1 __last1,
4375        _InputIterator2 __first2, _InputIterator2 __last2, _OutputIterator __result, _Compare __comp)
4376{
4377    for (; __first1 != __last1; ++__result)
4378    {
4379        if (__first2 == __last2)
4380            return _VSTD::copy(__first1, __last1, __result);
4381        if (__comp(*__first2, *__first1))
4382        {
4383            *__result = *__first2;
4384            ++__first2;
4385        }
4386        else
4387        {
4388            *__result = *__first1;
4389            ++__first1;
4390        }
4391    }
4392    return _VSTD::copy(__first2, __last2, __result);
4393}
4394
4395template <class _InputIterator1, class _InputIterator2, class _OutputIterator, class _Compare>
4396inline _LIBCPP_INLINE_VISIBILITY
4397_OutputIterator
4398merge(_InputIterator1 __first1, _InputIterator1 __last1,
4399      _InputIterator2 __first2, _InputIterator2 __last2, _OutputIterator __result, _Compare __comp)
4400{
4401    typedef typename __comp_ref_type<_Compare>::type _Comp_ref;
4402    return _VSTD::__merge<_Comp_ref>(__first1, __last1, __first2, __last2, __result, __comp);
4403}
4404
4405template <class _InputIterator1, class _InputIterator2, class _OutputIterator>
4406inline _LIBCPP_INLINE_VISIBILITY
4407_OutputIterator
4408merge(_InputIterator1 __first1, _InputIterator1 __last1,
4409      _InputIterator2 __first2, _InputIterator2 __last2, _OutputIterator __result)
4410{
4411    typedef typename iterator_traits<_InputIterator1>::value_type __v1;
4412    typedef typename iterator_traits<_InputIterator2>::value_type __v2;
4413    return _VSTD::merge(__first1, __last1, __first2, __last2, __result, __less<__v1, __v2>());
4414}
4415
4416// inplace_merge
4417
4418template <class _Compare, class _InputIterator1, class _InputIterator2,
4419          class _OutputIterator>
4420void __half_inplace_merge(_InputIterator1 __first1, _InputIterator1 __last1,
4421                          _InputIterator2 __first2, _InputIterator2 __last2,
4422                          _OutputIterator __result, _Compare __comp)
4423{
4424    for (; __first1 != __last1; ++__result)
4425    {
4426        if (__first2 == __last2)
4427        {
4428            _VSTD::move(__first1, __last1, __result);
4429            return;
4430        }
4431
4432        if (__comp(*__first2, *__first1))
4433        {
4434            *__result = _VSTD::move(*__first2);
4435            ++__first2;
4436        }
4437        else
4438        {
4439            *__result = _VSTD::move(*__first1);
4440            ++__first1;
4441        }
4442    }
4443    // __first2 through __last2 are already in the right spot.
4444}
4445
4446template <class _Compare, class _BidirectionalIterator>
4447void
4448__buffered_inplace_merge(_BidirectionalIterator __first, _BidirectionalIterator __middle, _BidirectionalIterator __last,
4449                _Compare __comp, typename iterator_traits<_BidirectionalIterator>::difference_type __len1,
4450                                 typename iterator_traits<_BidirectionalIterator>::difference_type __len2,
4451                typename iterator_traits<_BidirectionalIterator>::value_type* __buff)
4452{
4453    typedef typename iterator_traits<_BidirectionalIterator>::value_type value_type;
4454    __destruct_n __d(0);
4455    unique_ptr<value_type, __destruct_n&> __h2(__buff, __d);
4456    if (__len1 <= __len2)
4457    {
4458        value_type* __p = __buff;
4459        for (_BidirectionalIterator __i = __first; __i != __middle; __d.__incr((value_type*)0), (void) ++__i, (void) ++__p)
4460            ::new(__p) value_type(_VSTD::move(*__i));
4461        __half_inplace_merge(__buff, __p, __middle, __last, __first, __comp);
4462    }
4463    else
4464    {
4465        value_type* __p = __buff;
4466        for (_BidirectionalIterator __i = __middle; __i != __last; __d.__incr((value_type*)0), (void) ++__i, (void) ++__p)
4467            ::new(__p) value_type(_VSTD::move(*__i));
4468        typedef reverse_iterator<_BidirectionalIterator> _RBi;
4469        typedef reverse_iterator<value_type*> _Rv;
4470        __half_inplace_merge(_Rv(__p), _Rv(__buff),
4471                             _RBi(__middle), _RBi(__first),
4472                             _RBi(__last), __invert<_Compare>(__comp));
4473    }
4474}
4475
4476template <class _Compare, class _BidirectionalIterator>
4477void
4478__inplace_merge(_BidirectionalIterator __first, _BidirectionalIterator __middle, _BidirectionalIterator __last,
4479                _Compare __comp, typename iterator_traits<_BidirectionalIterator>::difference_type __len1,
4480                                 typename iterator_traits<_BidirectionalIterator>::difference_type __len2,
4481                typename iterator_traits<_BidirectionalIterator>::value_type* __buff, ptrdiff_t __buff_size)
4482{
4483    typedef typename iterator_traits<_BidirectionalIterator>::difference_type difference_type;
4484    while (true)
4485    {
4486        // if __middle == __last, we're done
4487        if (__len2 == 0)
4488            return;
4489        if (__len1 <= __buff_size || __len2 <= __buff_size)
4490            return __buffered_inplace_merge<_Compare>
4491                   (__first, __middle, __last, __comp, __len1, __len2, __buff);
4492        // shrink [__first, __middle) as much as possible (with no moves), returning if it shrinks to 0
4493        for (; true; ++__first, (void) --__len1)
4494        {
4495            if (__len1 == 0)
4496                return;
4497            if (__comp(*__middle, *__first))
4498                break;
4499        }
4500        // __first < __middle < __last
4501        // *__first > *__middle
4502        // partition [__first, __m1) [__m1, __middle) [__middle, __m2) [__m2, __last) such that
4503        //     all elements in:
4504        //         [__first, __m1)  <= [__middle, __m2)
4505        //         [__middle, __m2) <  [__m1, __middle)
4506        //         [__m1, __middle) <= [__m2, __last)
4507        //     and __m1 or __m2 is in the middle of its range
4508        _BidirectionalIterator __m1;  // "median" of [__first, __middle)
4509        _BidirectionalIterator __m2;  // "median" of [__middle, __last)
4510        difference_type __len11;      // distance(__first, __m1)
4511        difference_type __len21;      // distance(__middle, __m2)
4512        // binary search smaller range
4513        if (__len1 < __len2)
4514        {   // __len >= 1, __len2 >= 2
4515            __len21 = __len2 / 2;
4516            __m2 = __middle;
4517            _VSTD::advance(__m2, __len21);
4518            __m1 = __upper_bound<_Compare>(__first, __middle, *__m2, __comp);
4519            __len11 = _VSTD::distance(__first, __m1);
4520        }
4521        else
4522        {
4523            if (__len1 == 1)
4524            {   // __len1 >= __len2 && __len2 > 0, therefore __len2 == 1
4525                // It is known *__first > *__middle
4526                swap(*__first, *__middle);
4527                return;
4528            }
4529            // __len1 >= 2, __len2 >= 1
4530            __len11 = __len1 / 2;
4531            __m1 = __first;
4532            _VSTD::advance(__m1, __len11);
4533            __m2 = __lower_bound<_Compare>(__middle, __last, *__m1, __comp);
4534            __len21 = _VSTD::distance(__middle, __m2);
4535        }
4536        difference_type __len12 = __len1 - __len11;  // distance(__m1, __middle)
4537        difference_type __len22 = __len2 - __len21;  // distance(__m2, __last)
4538        // [__first, __m1) [__m1, __middle) [__middle, __m2) [__m2, __last)
4539        // swap middle two partitions
4540        __middle = _VSTD::rotate(__m1, __middle, __m2);
4541        // __len12 and __len21 now have swapped meanings
4542        // merge smaller range with recurisve call and larger with tail recursion elimination
4543        if (__len11 + __len21 < __len12 + __len22)
4544        {
4545            __inplace_merge<_Compare>(__first, __m1, __middle, __comp, __len11, __len21, __buff, __buff_size);
4546//          __inplace_merge<_Compare>(__middle, __m2, __last, __comp, __len12, __len22, __buff, __buff_size);
4547            __first = __middle;
4548            __middle = __m2;
4549            __len1 = __len12;
4550            __len2 = __len22;
4551        }
4552        else
4553        {
4554            __inplace_merge<_Compare>(__middle, __m2, __last, __comp, __len12, __len22, __buff, __buff_size);
4555//          __inplace_merge<_Compare>(__first, __m1, __middle, __comp, __len11, __len21, __buff, __buff_size);
4556            __last = __middle;
4557            __middle = __m1;
4558            __len1 = __len11;
4559            __len2 = __len21;
4560        }
4561    }
4562}
4563
4564template <class _BidirectionalIterator, class _Compare>
4565inline _LIBCPP_INLINE_VISIBILITY
4566void
4567inplace_merge(_BidirectionalIterator __first, _BidirectionalIterator __middle, _BidirectionalIterator __last,
4568              _Compare __comp)
4569{
4570    typedef typename iterator_traits<_BidirectionalIterator>::value_type value_type;
4571    typedef typename iterator_traits<_BidirectionalIterator>::difference_type difference_type;
4572    difference_type __len1 = _VSTD::distance(__first, __middle);
4573    difference_type __len2 = _VSTD::distance(__middle, __last);
4574    difference_type __buf_size = _VSTD::min(__len1, __len2);
4575    pair<value_type*, ptrdiff_t> __buf = _VSTD::get_temporary_buffer<value_type>(__buf_size);
4576    unique_ptr<value_type, __return_temporary_buffer> __h(__buf.first);
4577    typedef typename __comp_ref_type<_Compare>::type _Comp_ref;
4578    return _VSTD::__inplace_merge<_Comp_ref>(__first, __middle, __last, __comp, __len1, __len2,
4579                                            __buf.first, __buf.second);
4580}
4581
4582template <class _BidirectionalIterator>
4583inline _LIBCPP_INLINE_VISIBILITY
4584void
4585inplace_merge(_BidirectionalIterator __first, _BidirectionalIterator __middle, _BidirectionalIterator __last)
4586{
4587    _VSTD::inplace_merge(__first, __middle, __last,
4588                        __less<typename iterator_traits<_BidirectionalIterator>::value_type>());
4589}
4590
4591// stable_sort
4592
4593template <class _Compare, class _InputIterator1, class _InputIterator2>
4594void
4595__merge_move_construct(_InputIterator1 __first1, _InputIterator1 __last1,
4596        _InputIterator2 __first2, _InputIterator2 __last2,
4597        typename iterator_traits<_InputIterator1>::value_type* __result, _Compare __comp)
4598{
4599    typedef typename iterator_traits<_InputIterator1>::value_type value_type;
4600    __destruct_n __d(0);
4601    unique_ptr<value_type, __destruct_n&> __h(__result, __d);
4602    for (; true; ++__result)
4603    {
4604        if (__first1 == __last1)
4605        {
4606            for (; __first2 != __last2; ++__first2, ++__result, (void) __d.__incr((value_type*)0))
4607                ::new (__result) value_type(_VSTD::move(*__first2));
4608            __h.release();
4609            return;
4610        }
4611        if (__first2 == __last2)
4612        {
4613            for (; __first1 != __last1; ++__first1, ++__result, (void) __d.__incr((value_type*)0))
4614                ::new (__result) value_type(_VSTD::move(*__first1));
4615            __h.release();
4616            return;
4617        }
4618        if (__comp(*__first2, *__first1))
4619        {
4620            ::new (__result) value_type(_VSTD::move(*__first2));
4621            __d.__incr((value_type*)0);
4622            ++__first2;
4623        }
4624        else
4625        {
4626            ::new (__result) value_type(_VSTD::move(*__first1));
4627            __d.__incr((value_type*)0);
4628            ++__first1;
4629        }
4630    }
4631}
4632
4633template <class _Compare, class _InputIterator1, class _InputIterator2, class _OutputIterator>
4634void
4635__merge_move_assign(_InputIterator1 __first1, _InputIterator1 __last1,
4636        _InputIterator2 __first2, _InputIterator2 __last2,
4637        _OutputIterator __result, _Compare __comp)
4638{
4639    for (; __first1 != __last1; ++__result)
4640    {
4641        if (__first2 == __last2)
4642        {
4643            for (; __first1 != __last1; ++__first1, (void) ++__result)
4644                *__result = _VSTD::move(*__first1);
4645            return;
4646        }
4647        if (__comp(*__first2, *__first1))
4648        {
4649            *__result = _VSTD::move(*__first2);
4650            ++__first2;
4651        }
4652        else
4653        {
4654            *__result = _VSTD::move(*__first1);
4655            ++__first1;
4656        }
4657    }
4658    for (; __first2 != __last2; ++__first2, (void) ++__result)
4659        *__result = _VSTD::move(*__first2);
4660}
4661
4662template <class _Compare, class _RandomAccessIterator>
4663void
4664__stable_sort(_RandomAccessIterator __first, _RandomAccessIterator __last, _Compare __comp,
4665              typename iterator_traits<_RandomAccessIterator>::difference_type __len,
4666              typename iterator_traits<_RandomAccessIterator>::value_type* __buff, ptrdiff_t __buff_size);
4667
4668template <class _Compare, class _RandomAccessIterator>
4669void
4670__stable_sort_move(_RandomAccessIterator __first1, _RandomAccessIterator __last1, _Compare __comp,
4671                   typename iterator_traits<_RandomAccessIterator>::difference_type __len,
4672                   typename iterator_traits<_RandomAccessIterator>::value_type* __first2)
4673{
4674    typedef typename iterator_traits<_RandomAccessIterator>::value_type value_type;
4675    switch (__len)
4676    {
4677    case 0:
4678        return;
4679    case 1:
4680        ::new(__first2) value_type(_VSTD::move(*__first1));
4681        return;
4682    case 2:
4683        __destruct_n __d(0);
4684        unique_ptr<value_type, __destruct_n&> __h2(__first2, __d);
4685        if (__comp(*--__last1, *__first1))
4686        {
4687            ::new(__first2) value_type(_VSTD::move(*__last1));
4688            __d.__incr((value_type*)0);
4689            ++__first2;
4690            ::new(__first2) value_type(_VSTD::move(*__first1));
4691        }
4692        else
4693        {
4694            ::new(__first2) value_type(_VSTD::move(*__first1));
4695            __d.__incr((value_type*)0);
4696            ++__first2;
4697            ::new(__first2) value_type(_VSTD::move(*__last1));
4698        }
4699        __h2.release();
4700        return;
4701    }
4702    if (__len <= 8)
4703    {
4704        __insertion_sort_move<_Compare>(__first1, __last1, __first2, __comp);
4705        return;
4706    }
4707    typename iterator_traits<_RandomAccessIterator>::difference_type __l2 = __len / 2;
4708    _RandomAccessIterator __m = __first1 + __l2;
4709    __stable_sort<_Compare>(__first1, __m, __comp, __l2, __first2, __l2);
4710    __stable_sort<_Compare>(__m, __last1, __comp, __len - __l2, __first2 + __l2, __len - __l2);
4711    __merge_move_construct<_Compare>(__first1, __m, __m, __last1, __first2, __comp);
4712}
4713
4714template <class _Tp>
4715struct __stable_sort_switch
4716{
4717    static const unsigned value = 128*is_trivially_copy_assignable<_Tp>::value;
4718};
4719
4720template <class _Compare, class _RandomAccessIterator>
4721void
4722__stable_sort(_RandomAccessIterator __first, _RandomAccessIterator __last, _Compare __comp,
4723              typename iterator_traits<_RandomAccessIterator>::difference_type __len,
4724              typename iterator_traits<_RandomAccessIterator>::value_type* __buff, ptrdiff_t __buff_size)
4725{
4726    typedef typename iterator_traits<_RandomAccessIterator>::value_type value_type;
4727    typedef typename iterator_traits<_RandomAccessIterator>::difference_type difference_type;
4728    switch (__len)
4729    {
4730    case 0:
4731    case 1:
4732        return;
4733    case 2:
4734        if (__comp(*--__last, *__first))
4735            swap(*__first, *__last);
4736        return;
4737    }
4738    if (__len <= static_cast<difference_type>(__stable_sort_switch<value_type>::value))
4739    {
4740        __insertion_sort<_Compare>(__first, __last, __comp);
4741        return;
4742    }
4743    typename iterator_traits<_RandomAccessIterator>::difference_type __l2 = __len / 2;
4744    _RandomAccessIterator __m = __first + __l2;
4745    if (__len <= __buff_size)
4746    {
4747        __destruct_n __d(0);
4748        unique_ptr<value_type, __destruct_n&> __h2(__buff, __d);
4749        __stable_sort_move<_Compare>(__first, __m, __comp, __l2, __buff);
4750        __d.__set(__l2, (value_type*)0);
4751        __stable_sort_move<_Compare>(__m, __last, __comp, __len - __l2, __buff + __l2);
4752        __d.__set(__len, (value_type*)0);
4753        __merge_move_assign<_Compare>(__buff, __buff + __l2, __buff + __l2, __buff + __len, __first, __comp);
4754//         __merge<_Compare>(move_iterator<value_type*>(__buff),
4755//                           move_iterator<value_type*>(__buff + __l2),
4756//                           move_iterator<_RandomAccessIterator>(__buff + __l2),
4757//                           move_iterator<_RandomAccessIterator>(__buff + __len),
4758//                           __first, __comp);
4759        return;
4760    }
4761    __stable_sort<_Compare>(__first, __m, __comp, __l2, __buff, __buff_size);
4762    __stable_sort<_Compare>(__m, __last, __comp, __len - __l2, __buff, __buff_size);
4763    __inplace_merge<_Compare>(__first, __m, __last, __comp, __l2, __len - __l2, __buff, __buff_size);
4764}
4765
4766template <class _RandomAccessIterator, class _Compare>
4767inline _LIBCPP_INLINE_VISIBILITY
4768void
4769stable_sort(_RandomAccessIterator __first, _RandomAccessIterator __last, _Compare __comp)
4770{
4771    typedef typename iterator_traits<_RandomAccessIterator>::value_type value_type;
4772    typedef typename iterator_traits<_RandomAccessIterator>::difference_type difference_type;
4773    difference_type __len = __last - __first;
4774    pair<value_type*, ptrdiff_t> __buf(0, 0);
4775    unique_ptr<value_type, __return_temporary_buffer> __h;
4776    if (__len > static_cast<difference_type>(__stable_sort_switch<value_type>::value))
4777    {
4778        __buf = _VSTD::get_temporary_buffer<value_type>(__len);
4779        __h.reset(__buf.first);
4780    }
4781    typedef typename __comp_ref_type<_Compare>::type _Comp_ref;
4782    __stable_sort<_Comp_ref>(__first, __last, __comp, __len, __buf.first, __buf.second);
4783}
4784
4785template <class _RandomAccessIterator>
4786inline _LIBCPP_INLINE_VISIBILITY
4787void
4788stable_sort(_RandomAccessIterator __first, _RandomAccessIterator __last)
4789{
4790    _VSTD::stable_sort(__first, __last, __less<typename iterator_traits<_RandomAccessIterator>::value_type>());
4791}
4792
4793// is_heap_until
4794
4795template <class _RandomAccessIterator, class _Compare>
4796_LIBCPP_NODISCARD_EXT _LIBCPP_CONSTEXPR_AFTER_CXX17 _RandomAccessIterator
4797is_heap_until(_RandomAccessIterator __first, _RandomAccessIterator __last, _Compare __comp)
4798{
4799    typedef typename _VSTD::iterator_traits<_RandomAccessIterator>::difference_type difference_type;
4800    difference_type __len = __last - __first;
4801    difference_type __p = 0;
4802    difference_type __c = 1;
4803    _RandomAccessIterator __pp = __first;
4804    while (__c < __len)
4805    {
4806        _RandomAccessIterator __cp = __first + __c;
4807        if (__comp(*__pp, *__cp))
4808            return __cp;
4809        ++__c;
4810        ++__cp;
4811        if (__c == __len)
4812            return __last;
4813        if (__comp(*__pp, *__cp))
4814            return __cp;
4815        ++__p;
4816        ++__pp;
4817        __c = 2 * __p + 1;
4818    }
4819    return __last;
4820}
4821
4822template<class _RandomAccessIterator>
4823_LIBCPP_NODISCARD_EXT inline
4824_LIBCPP_INLINE_VISIBILITY _LIBCPP_CONSTEXPR_AFTER_CXX17
4825_RandomAccessIterator
4826is_heap_until(_RandomAccessIterator __first, _RandomAccessIterator __last)
4827{
4828    return _VSTD::is_heap_until(__first, __last, __less<typename iterator_traits<_RandomAccessIterator>::value_type>());
4829}
4830
4831// is_heap
4832
4833template <class _RandomAccessIterator, class _Compare>
4834_LIBCPP_NODISCARD_EXT inline
4835_LIBCPP_INLINE_VISIBILITY _LIBCPP_CONSTEXPR_AFTER_CXX17
4836bool
4837is_heap(_RandomAccessIterator __first, _RandomAccessIterator __last, _Compare __comp)
4838{
4839    return _VSTD::is_heap_until(__first, __last, __comp) == __last;
4840}
4841
4842template<class _RandomAccessIterator>
4843_LIBCPP_NODISCARD_EXT inline
4844_LIBCPP_INLINE_VISIBILITY _LIBCPP_CONSTEXPR_AFTER_CXX17
4845bool
4846is_heap(_RandomAccessIterator __first, _RandomAccessIterator __last)
4847{
4848    return _VSTD::is_heap(__first, __last, __less<typename iterator_traits<_RandomAccessIterator>::value_type>());
4849}
4850
4851// push_heap
4852
4853template <class _Compare, class _RandomAccessIterator>
4854void
4855__sift_up(_RandomAccessIterator __first, _RandomAccessIterator __last, _Compare __comp,
4856          typename iterator_traits<_RandomAccessIterator>::difference_type __len)
4857{
4858    typedef typename iterator_traits<_RandomAccessIterator>::value_type value_type;
4859    if (__len > 1)
4860    {
4861        __len = (__len - 2) / 2;
4862        _RandomAccessIterator __ptr = __first + __len;
4863        if (__comp(*__ptr, *--__last))
4864        {
4865            value_type __t(_VSTD::move(*__last));
4866            do
4867            {
4868                *__last = _VSTD::move(*__ptr);
4869                __last = __ptr;
4870                if (__len == 0)
4871                    break;
4872                __len = (__len - 1) / 2;
4873                __ptr = __first + __len;
4874            } while (__comp(*__ptr, __t));
4875            *__last = _VSTD::move(__t);
4876        }
4877    }
4878}
4879
4880template <class _RandomAccessIterator, class _Compare>
4881inline _LIBCPP_INLINE_VISIBILITY
4882void
4883push_heap(_RandomAccessIterator __first, _RandomAccessIterator __last, _Compare __comp)
4884{
4885    typedef typename __comp_ref_type<_Compare>::type _Comp_ref;
4886    __sift_up<_Comp_ref>(__first, __last, __comp, __last - __first);
4887}
4888
4889template <class _RandomAccessIterator>
4890inline _LIBCPP_INLINE_VISIBILITY
4891void
4892push_heap(_RandomAccessIterator __first, _RandomAccessIterator __last)
4893{
4894    _VSTD::push_heap(__first, __last, __less<typename iterator_traits<_RandomAccessIterator>::value_type>());
4895}
4896
4897// pop_heap
4898
4899template <class _Compare, class _RandomAccessIterator>
4900void
4901__sift_down(_RandomAccessIterator __first, _RandomAccessIterator /*__last*/,
4902            _Compare __comp,
4903            typename iterator_traits<_RandomAccessIterator>::difference_type __len,
4904            _RandomAccessIterator __start)
4905{
4906    typedef typename iterator_traits<_RandomAccessIterator>::difference_type difference_type;
4907    typedef typename iterator_traits<_RandomAccessIterator>::value_type value_type;
4908    // left-child of __start is at 2 * __start + 1
4909    // right-child of __start is at 2 * __start + 2
4910    difference_type __child = __start - __first;
4911
4912    if (__len < 2 || (__len - 2) / 2 < __child)
4913        return;
4914
4915    __child = 2 * __child + 1;
4916    _RandomAccessIterator __child_i = __first + __child;
4917
4918    if ((__child + 1) < __len && __comp(*__child_i, *(__child_i + 1))) {
4919        // right-child exists and is greater than left-child
4920        ++__child_i;
4921        ++__child;
4922    }
4923
4924    // check if we are in heap-order
4925    if (__comp(*__child_i, *__start))
4926        // we are, __start is larger than it's largest child
4927        return;
4928
4929    value_type __top(_VSTD::move(*__start));
4930    do
4931    {
4932        // we are not in heap-order, swap the parent with it's largest child
4933        *__start = _VSTD::move(*__child_i);
4934        __start = __child_i;
4935
4936        if ((__len - 2) / 2 < __child)
4937            break;
4938
4939        // recompute the child based off of the updated parent
4940        __child = 2 * __child + 1;
4941        __child_i = __first + __child;
4942
4943        if ((__child + 1) < __len && __comp(*__child_i, *(__child_i + 1))) {
4944            // right-child exists and is greater than left-child
4945            ++__child_i;
4946            ++__child;
4947        }
4948
4949        // check if we are in heap-order
4950    } while (!__comp(*__child_i, __top));
4951    *__start = _VSTD::move(__top);
4952}
4953
4954template <class _Compare, class _RandomAccessIterator>
4955inline _LIBCPP_INLINE_VISIBILITY
4956void
4957__pop_heap(_RandomAccessIterator __first, _RandomAccessIterator __last, _Compare __comp,
4958           typename iterator_traits<_RandomAccessIterator>::difference_type __len)
4959{
4960    if (__len > 1)
4961    {
4962        swap(*__first, *--__last);
4963        __sift_down<_Compare>(__first, __last, __comp, __len - 1, __first);
4964    }
4965}
4966
4967template <class _RandomAccessIterator, class _Compare>
4968inline _LIBCPP_INLINE_VISIBILITY
4969void
4970pop_heap(_RandomAccessIterator __first, _RandomAccessIterator __last, _Compare __comp)
4971{
4972    typedef typename __comp_ref_type<_Compare>::type _Comp_ref;
4973    __pop_heap<_Comp_ref>(__first, __last, __comp, __last - __first);
4974}
4975
4976template <class _RandomAccessIterator>
4977inline _LIBCPP_INLINE_VISIBILITY
4978void
4979pop_heap(_RandomAccessIterator __first, _RandomAccessIterator __last)
4980{
4981    _VSTD::pop_heap(__first, __last, __less<typename iterator_traits<_RandomAccessIterator>::value_type>());
4982}
4983
4984// make_heap
4985
4986template <class _Compare, class _RandomAccessIterator>
4987void
4988__make_heap(_RandomAccessIterator __first, _RandomAccessIterator __last, _Compare __comp)
4989{
4990    typedef typename iterator_traits<_RandomAccessIterator>::difference_type difference_type;
4991    difference_type __n = __last - __first;
4992    if (__n > 1)
4993    {
4994        // start from the first parent, there is no need to consider children
4995        for (difference_type __start = (__n - 2) / 2; __start >= 0; --__start)
4996        {
4997            __sift_down<_Compare>(__first, __last, __comp, __n, __first + __start);
4998        }
4999    }
5000}
5001
5002template <class _RandomAccessIterator, class _Compare>
5003inline _LIBCPP_INLINE_VISIBILITY
5004void
5005make_heap(_RandomAccessIterator __first, _RandomAccessIterator __last, _Compare __comp)
5006{
5007    typedef typename __comp_ref_type<_Compare>::type _Comp_ref;
5008    __make_heap<_Comp_ref>(__first, __last, __comp);
5009}
5010
5011template <class _RandomAccessIterator>
5012inline _LIBCPP_INLINE_VISIBILITY
5013void
5014make_heap(_RandomAccessIterator __first, _RandomAccessIterator __last)
5015{
5016    _VSTD::make_heap(__first, __last, __less<typename iterator_traits<_RandomAccessIterator>::value_type>());
5017}
5018
5019// sort_heap
5020
5021template <class _Compare, class _RandomAccessIterator>
5022void
5023__sort_heap(_RandomAccessIterator __first, _RandomAccessIterator __last, _Compare __comp)
5024{
5025    typedef typename iterator_traits<_RandomAccessIterator>::difference_type difference_type;
5026    for (difference_type __n = __last - __first; __n > 1; --__last, (void) --__n)
5027        __pop_heap<_Compare>(__first, __last, __comp, __n);
5028}
5029
5030template <class _RandomAccessIterator, class _Compare>
5031inline _LIBCPP_INLINE_VISIBILITY
5032void
5033sort_heap(_RandomAccessIterator __first, _RandomAccessIterator __last, _Compare __comp)
5034{
5035    typedef typename __comp_ref_type<_Compare>::type _Comp_ref;
5036    __sort_heap<_Comp_ref>(__first, __last, __comp);
5037}
5038
5039template <class _RandomAccessIterator>
5040inline _LIBCPP_INLINE_VISIBILITY
5041void
5042sort_heap(_RandomAccessIterator __first, _RandomAccessIterator __last)
5043{
5044    _VSTD::sort_heap(__first, __last, __less<typename iterator_traits<_RandomAccessIterator>::value_type>());
5045}
5046
5047// partial_sort
5048
5049template <class _Compare, class _RandomAccessIterator>
5050void
5051__partial_sort(_RandomAccessIterator __first, _RandomAccessIterator __middle, _RandomAccessIterator __last,
5052             _Compare __comp)
5053{
5054    __make_heap<_Compare>(__first, __middle, __comp);
5055    typename iterator_traits<_RandomAccessIterator>::difference_type __len = __middle - __first;
5056    for (_RandomAccessIterator __i = __middle; __i != __last; ++__i)
5057    {
5058        if (__comp(*__i, *__first))
5059        {
5060            swap(*__i, *__first);
5061            __sift_down<_Compare>(__first, __middle, __comp, __len, __first);
5062        }
5063    }
5064    __sort_heap<_Compare>(__first, __middle, __comp);
5065}
5066
5067template <class _RandomAccessIterator, class _Compare>
5068inline _LIBCPP_INLINE_VISIBILITY
5069void
5070partial_sort(_RandomAccessIterator __first, _RandomAccessIterator __middle, _RandomAccessIterator __last,
5071             _Compare __comp)
5072{
5073    typedef typename __comp_ref_type<_Compare>::type _Comp_ref;
5074    __partial_sort<_Comp_ref>(__first, __middle, __last, __comp);
5075}
5076
5077template <class _RandomAccessIterator>
5078inline _LIBCPP_INLINE_VISIBILITY
5079void
5080partial_sort(_RandomAccessIterator __first, _RandomAccessIterator __middle, _RandomAccessIterator __last)
5081{
5082    _VSTD::partial_sort(__first, __middle, __last,
5083                       __less<typename iterator_traits<_RandomAccessIterator>::value_type>());
5084}
5085
5086// partial_sort_copy
5087
5088template <class _Compare, class _InputIterator, class _RandomAccessIterator>
5089_RandomAccessIterator
5090__partial_sort_copy(_InputIterator __first, _InputIterator __last,
5091                    _RandomAccessIterator __result_first, _RandomAccessIterator __result_last, _Compare __comp)
5092{
5093    _RandomAccessIterator __r = __result_first;
5094    if (__r != __result_last)
5095    {
5096        for (; __first != __last && __r != __result_last; ++__first, (void) ++__r)
5097            *__r = *__first;
5098        __make_heap<_Compare>(__result_first, __r, __comp);
5099        typename iterator_traits<_RandomAccessIterator>::difference_type __len = __r - __result_first;
5100        for (; __first != __last; ++__first)
5101            if (__comp(*__first, *__result_first))
5102            {
5103                *__result_first = *__first;
5104                __sift_down<_Compare>(__result_first, __r, __comp, __len, __result_first);
5105            }
5106        __sort_heap<_Compare>(__result_first, __r, __comp);
5107    }
5108    return __r;
5109}
5110
5111template <class _InputIterator, class _RandomAccessIterator, class _Compare>
5112inline _LIBCPP_INLINE_VISIBILITY
5113_RandomAccessIterator
5114partial_sort_copy(_InputIterator __first, _InputIterator __last,
5115                  _RandomAccessIterator __result_first, _RandomAccessIterator __result_last, _Compare __comp)
5116{
5117    typedef typename __comp_ref_type<_Compare>::type _Comp_ref;
5118    return __partial_sort_copy<_Comp_ref>(__first, __last, __result_first, __result_last, __comp);
5119}
5120
5121template <class _InputIterator, class _RandomAccessIterator>
5122inline _LIBCPP_INLINE_VISIBILITY
5123_RandomAccessIterator
5124partial_sort_copy(_InputIterator __first, _InputIterator __last,
5125                  _RandomAccessIterator __result_first, _RandomAccessIterator __result_last)
5126{
5127    return _VSTD::partial_sort_copy(__first, __last, __result_first, __result_last,
5128                                   __less<typename iterator_traits<_RandomAccessIterator>::value_type>());
5129}
5130
5131// nth_element
5132
5133template <class _Compare, class _RandomAccessIterator>
5134void
5135__nth_element(_RandomAccessIterator __first, _RandomAccessIterator __nth, _RandomAccessIterator __last, _Compare __comp)
5136{
5137    // _Compare is known to be a reference type
5138    typedef typename iterator_traits<_RandomAccessIterator>::difference_type difference_type;
5139    const difference_type __limit = 7;
5140    while (true)
5141    {
5142    __restart:
5143        if (__nth == __last)
5144            return;
5145        difference_type __len = __last - __first;
5146        switch (__len)
5147        {
5148        case 0:
5149        case 1:
5150            return;
5151        case 2:
5152            if (__comp(*--__last, *__first))
5153                swap(*__first, *__last);
5154            return;
5155        case 3:
5156            {
5157            _RandomAccessIterator __m = __first;
5158            _VSTD::__sort3<_Compare>(__first, ++__m, --__last, __comp);
5159            return;
5160            }
5161        }
5162        if (__len <= __limit)
5163        {
5164            __selection_sort<_Compare>(__first, __last, __comp);
5165            return;
5166        }
5167        // __len > __limit >= 3
5168        _RandomAccessIterator __m = __first + __len/2;
5169        _RandomAccessIterator __lm1 = __last;
5170        unsigned __n_swaps = _VSTD::__sort3<_Compare>(__first, __m, --__lm1, __comp);
5171        // *__m is median
5172        // partition [__first, __m) < *__m and *__m <= [__m, __last)
5173        // (this inhibits tossing elements equivalent to __m around unnecessarily)
5174        _RandomAccessIterator __i = __first;
5175        _RandomAccessIterator __j = __lm1;
5176        // j points beyond range to be tested, *__lm1 is known to be <= *__m
5177        // The search going up is known to be guarded but the search coming down isn't.
5178        // Prime the downward search with a guard.
5179        if (!__comp(*__i, *__m))  // if *__first == *__m
5180        {
5181            // *__first == *__m, *__first doesn't go in first part
5182            // manually guard downward moving __j against __i
5183            while (true)
5184            {
5185                if (__i == --__j)
5186                {
5187                    // *__first == *__m, *__m <= all other elements
5188                    // Parition instead into [__first, __i) == *__first and *__first < [__i, __last)
5189                    ++__i;  // __first + 1
5190                    __j = __last;
5191                    if (!__comp(*__first, *--__j))  // we need a guard if *__first == *(__last-1)
5192                    {
5193                        while (true)
5194                        {
5195                            if (__i == __j)
5196                                return;  // [__first, __last) all equivalent elements
5197                            if (__comp(*__first, *__i))
5198                            {
5199                                swap(*__i, *__j);
5200                                ++__n_swaps;
5201                                ++__i;
5202                                break;
5203                            }
5204                            ++__i;
5205                        }
5206                    }
5207                    // [__first, __i) == *__first and *__first < [__j, __last) and __j == __last - 1
5208                    if (__i == __j)
5209                        return;
5210                    while (true)
5211                    {
5212                        while (!__comp(*__first, *__i))
5213                            ++__i;
5214                        while (__comp(*__first, *--__j))
5215                            ;
5216                        if (__i >= __j)
5217                            break;
5218                        swap(*__i, *__j);
5219                        ++__n_swaps;
5220                        ++__i;
5221                    }
5222                    // [__first, __i) == *__first and *__first < [__i, __last)
5223                    // The first part is sorted,
5224                    if (__nth < __i)
5225                        return;
5226                    // __nth_element the secod part
5227                    // __nth_element<_Compare>(__i, __nth, __last, __comp);
5228                    __first = __i;
5229                    goto __restart;
5230                }
5231                if (__comp(*__j, *__m))
5232                {
5233                    swap(*__i, *__j);
5234                    ++__n_swaps;
5235                    break;  // found guard for downward moving __j, now use unguarded partition
5236                }
5237            }
5238        }
5239        ++__i;
5240        // j points beyond range to be tested, *__lm1 is known to be <= *__m
5241        // if not yet partitioned...
5242        if (__i < __j)
5243        {
5244            // known that *(__i - 1) < *__m
5245            while (true)
5246            {
5247                // __m still guards upward moving __i
5248                while (__comp(*__i, *__m))
5249                    ++__i;
5250                // It is now known that a guard exists for downward moving __j
5251                while (!__comp(*--__j, *__m))
5252                    ;
5253                if (__i >= __j)
5254                    break;
5255                swap(*__i, *__j);
5256                ++__n_swaps;
5257                // It is known that __m != __j
5258                // If __m just moved, follow it
5259                if (__m == __i)
5260                    __m = __j;
5261                ++__i;
5262            }
5263        }
5264        // [__first, __i) < *__m and *__m <= [__i, __last)
5265        if (__i != __m && __comp(*__m, *__i))
5266        {
5267            swap(*__i, *__m);
5268            ++__n_swaps;
5269        }
5270        // [__first, __i) < *__i and *__i <= [__i+1, __last)
5271        if (__nth == __i)
5272            return;
5273        if (__n_swaps == 0)
5274        {
5275            // We were given a perfectly partitioned sequence.  Coincidence?
5276            if (__nth < __i)
5277            {
5278                // Check for [__first, __i) already sorted
5279                __j = __m = __first;
5280                while (++__j != __i)
5281                {
5282                    if (__comp(*__j, *__m))
5283                        // not yet sorted, so sort
5284                        goto not_sorted;
5285                    __m = __j;
5286                }
5287                // [__first, __i) sorted
5288                return;
5289            }
5290            else
5291            {
5292                // Check for [__i, __last) already sorted
5293                __j = __m = __i;
5294                while (++__j != __last)
5295                {
5296                    if (__comp(*__j, *__m))
5297                        // not yet sorted, so sort
5298                        goto not_sorted;
5299                    __m = __j;
5300                }
5301                // [__i, __last) sorted
5302                return;
5303            }
5304        }
5305not_sorted:
5306        // __nth_element on range containing __nth
5307        if (__nth < __i)
5308        {
5309            // __nth_element<_Compare>(__first, __nth, __i, __comp);
5310            __last = __i;
5311        }
5312        else
5313        {
5314            // __nth_element<_Compare>(__i+1, __nth, __last, __comp);
5315            __first = ++__i;
5316        }
5317    }
5318}
5319
5320template <class _RandomAccessIterator, class _Compare>
5321inline _LIBCPP_INLINE_VISIBILITY
5322void
5323nth_element(_RandomAccessIterator __first, _RandomAccessIterator __nth, _RandomAccessIterator __last, _Compare __comp)
5324{
5325    typedef typename __comp_ref_type<_Compare>::type _Comp_ref;
5326    __nth_element<_Comp_ref>(__first, __nth, __last, __comp);
5327}
5328
5329template <class _RandomAccessIterator>
5330inline _LIBCPP_INLINE_VISIBILITY
5331void
5332nth_element(_RandomAccessIterator __first, _RandomAccessIterator __nth, _RandomAccessIterator __last)
5333{
5334    _VSTD::nth_element(__first, __nth, __last, __less<typename iterator_traits<_RandomAccessIterator>::value_type>());
5335}
5336
5337// includes
5338
5339template <class _Compare, class _InputIterator1, class _InputIterator2>
5340_LIBCPP_CONSTEXPR_AFTER_CXX17 bool
5341__includes(_InputIterator1 __first1, _InputIterator1 __last1, _InputIterator2 __first2, _InputIterator2 __last2,
5342           _Compare __comp)
5343{
5344    for (; __first2 != __last2; ++__first1)
5345    {
5346        if (__first1 == __last1 || __comp(*__first2, *__first1))
5347            return false;
5348        if (!__comp(*__first1, *__first2))
5349            ++__first2;
5350    }
5351    return true;
5352}
5353
5354template <class _InputIterator1, class _InputIterator2, class _Compare>
5355_LIBCPP_NODISCARD_EXT inline
5356_LIBCPP_INLINE_VISIBILITY _LIBCPP_CONSTEXPR_AFTER_CXX17
5357bool
5358includes(_InputIterator1 __first1, _InputIterator1 __last1, _InputIterator2 __first2, _InputIterator2 __last2,
5359         _Compare __comp)
5360{
5361    typedef typename __comp_ref_type<_Compare>::type _Comp_ref;
5362    return __includes<_Comp_ref>(__first1, __last1, __first2, __last2, __comp);
5363}
5364
5365template <class _InputIterator1, class _InputIterator2>
5366_LIBCPP_NODISCARD_EXT inline
5367_LIBCPP_INLINE_VISIBILITY _LIBCPP_CONSTEXPR_AFTER_CXX17
5368bool
5369includes(_InputIterator1 __first1, _InputIterator1 __last1, _InputIterator2 __first2, _InputIterator2 __last2)
5370{
5371    return _VSTD::includes(__first1, __last1, __first2, __last2,
5372                          __less<typename iterator_traits<_InputIterator1>::value_type,
5373                                 typename iterator_traits<_InputIterator2>::value_type>());
5374}
5375
5376// set_union
5377
5378template <class _Compare, class _InputIterator1, class _InputIterator2, class _OutputIterator>
5379_OutputIterator
5380__set_union(_InputIterator1 __first1, _InputIterator1 __last1,
5381            _InputIterator2 __first2, _InputIterator2 __last2, _OutputIterator __result, _Compare __comp)
5382{
5383    for (; __first1 != __last1; ++__result)
5384    {
5385        if (__first2 == __last2)
5386            return _VSTD::copy(__first1, __last1, __result);
5387        if (__comp(*__first2, *__first1))
5388        {
5389            *__result = *__first2;
5390            ++__first2;
5391        }
5392        else
5393        {
5394            if (!__comp(*__first1, *__first2))
5395                ++__first2;
5396            *__result = *__first1;
5397            ++__first1;
5398        }
5399    }
5400    return _VSTD::copy(__first2, __last2, __result);
5401}
5402
5403template <class _InputIterator1, class _InputIterator2, class _OutputIterator, class _Compare>
5404inline _LIBCPP_INLINE_VISIBILITY
5405_OutputIterator
5406set_union(_InputIterator1 __first1, _InputIterator1 __last1,
5407          _InputIterator2 __first2, _InputIterator2 __last2, _OutputIterator __result, _Compare __comp)
5408{
5409    typedef typename __comp_ref_type<_Compare>::type _Comp_ref;
5410    return __set_union<_Comp_ref>(__first1, __last1, __first2, __last2, __result, __comp);
5411}
5412
5413template <class _InputIterator1, class _InputIterator2, class _OutputIterator>
5414inline _LIBCPP_INLINE_VISIBILITY
5415_OutputIterator
5416set_union(_InputIterator1 __first1, _InputIterator1 __last1,
5417          _InputIterator2 __first2, _InputIterator2 __last2, _OutputIterator __result)
5418{
5419    return _VSTD::set_union(__first1, __last1, __first2, __last2, __result,
5420                          __less<typename iterator_traits<_InputIterator1>::value_type,
5421                                 typename iterator_traits<_InputIterator2>::value_type>());
5422}
5423
5424// set_intersection
5425
5426template <class _Compare, class _InputIterator1, class _InputIterator2, class _OutputIterator>
5427_LIBCPP_CONSTEXPR_AFTER_CXX17 _OutputIterator
5428__set_intersection(_InputIterator1 __first1, _InputIterator1 __last1,
5429                   _InputIterator2 __first2, _InputIterator2 __last2, _OutputIterator __result, _Compare __comp)
5430{
5431    while (__first1 != __last1 && __first2 != __last2)
5432    {
5433        if (__comp(*__first1, *__first2))
5434            ++__first1;
5435        else
5436        {
5437            if (!__comp(*__first2, *__first1))
5438            {
5439                *__result = *__first1;
5440                ++__result;
5441                ++__first1;
5442            }
5443            ++__first2;
5444        }
5445    }
5446    return __result;
5447}
5448
5449template <class _InputIterator1, class _InputIterator2, class _OutputIterator, class _Compare>
5450inline _LIBCPP_INLINE_VISIBILITY _LIBCPP_CONSTEXPR_AFTER_CXX17
5451_OutputIterator
5452set_intersection(_InputIterator1 __first1, _InputIterator1 __last1,
5453                 _InputIterator2 __first2, _InputIterator2 __last2, _OutputIterator __result, _Compare __comp)
5454{
5455    typedef typename __comp_ref_type<_Compare>::type _Comp_ref;
5456    return __set_intersection<_Comp_ref>(__first1, __last1, __first2, __last2, __result, __comp);
5457}
5458
5459template <class _InputIterator1, class _InputIterator2, class _OutputIterator>
5460inline _LIBCPP_INLINE_VISIBILITY _LIBCPP_CONSTEXPR_AFTER_CXX17
5461_OutputIterator
5462set_intersection(_InputIterator1 __first1, _InputIterator1 __last1,
5463                 _InputIterator2 __first2, _InputIterator2 __last2, _OutputIterator __result)
5464{
5465    return _VSTD::set_intersection(__first1, __last1, __first2, __last2, __result,
5466                                  __less<typename iterator_traits<_InputIterator1>::value_type,
5467                                         typename iterator_traits<_InputIterator2>::value_type>());
5468}
5469
5470// set_difference
5471
5472template <class _Compare, class _InputIterator1, class _InputIterator2, class _OutputIterator>
5473_OutputIterator
5474__set_difference(_InputIterator1 __first1, _InputIterator1 __last1,
5475                 _InputIterator2 __first2, _InputIterator2 __last2, _OutputIterator __result, _Compare __comp)
5476{
5477    while (__first1 != __last1)
5478    {
5479        if (__first2 == __last2)
5480            return _VSTD::copy(__first1, __last1, __result);
5481        if (__comp(*__first1, *__first2))
5482        {
5483            *__result = *__first1;
5484            ++__result;
5485            ++__first1;
5486        }
5487        else
5488        {
5489            if (!__comp(*__first2, *__first1))
5490                ++__first1;
5491            ++__first2;
5492        }
5493    }
5494    return __result;
5495}
5496
5497template <class _InputIterator1, class _InputIterator2, class _OutputIterator, class _Compare>
5498inline _LIBCPP_INLINE_VISIBILITY
5499_OutputIterator
5500set_difference(_InputIterator1 __first1, _InputIterator1 __last1,
5501               _InputIterator2 __first2, _InputIterator2 __last2, _OutputIterator __result, _Compare __comp)
5502{
5503    typedef typename __comp_ref_type<_Compare>::type _Comp_ref;
5504    return __set_difference<_Comp_ref>(__first1, __last1, __first2, __last2, __result, __comp);
5505}
5506
5507template <class _InputIterator1, class _InputIterator2, class _OutputIterator>
5508inline _LIBCPP_INLINE_VISIBILITY
5509_OutputIterator
5510set_difference(_InputIterator1 __first1, _InputIterator1 __last1,
5511               _InputIterator2 __first2, _InputIterator2 __last2, _OutputIterator __result)
5512{
5513    return _VSTD::set_difference(__first1, __last1, __first2, __last2, __result,
5514                                __less<typename iterator_traits<_InputIterator1>::value_type,
5515                                       typename iterator_traits<_InputIterator2>::value_type>());
5516}
5517
5518// set_symmetric_difference
5519
5520template <class _Compare, class _InputIterator1, class _InputIterator2, class _OutputIterator>
5521_OutputIterator
5522__set_symmetric_difference(_InputIterator1 __first1, _InputIterator1 __last1,
5523                           _InputIterator2 __first2, _InputIterator2 __last2, _OutputIterator __result, _Compare __comp)
5524{
5525    while (__first1 != __last1)
5526    {
5527        if (__first2 == __last2)
5528            return _VSTD::copy(__first1, __last1, __result);
5529        if (__comp(*__first1, *__first2))
5530        {
5531            *__result = *__first1;
5532            ++__result;
5533            ++__first1;
5534        }
5535        else
5536        {
5537            if (__comp(*__first2, *__first1))
5538            {
5539                *__result = *__first2;
5540                ++__result;
5541            }
5542            else
5543                ++__first1;
5544            ++__first2;
5545        }
5546    }
5547    return _VSTD::copy(__first2, __last2, __result);
5548}
5549
5550template <class _InputIterator1, class _InputIterator2, class _OutputIterator, class _Compare>
5551inline _LIBCPP_INLINE_VISIBILITY
5552_OutputIterator
5553set_symmetric_difference(_InputIterator1 __first1, _InputIterator1 __last1,
5554                         _InputIterator2 __first2, _InputIterator2 __last2, _OutputIterator __result, _Compare __comp)
5555{
5556    typedef typename __comp_ref_type<_Compare>::type _Comp_ref;
5557    return __set_symmetric_difference<_Comp_ref>(__first1, __last1, __first2, __last2, __result, __comp);
5558}
5559
5560template <class _InputIterator1, class _InputIterator2, class _OutputIterator>
5561inline _LIBCPP_INLINE_VISIBILITY
5562_OutputIterator
5563set_symmetric_difference(_InputIterator1 __first1, _InputIterator1 __last1,
5564                         _InputIterator2 __first2, _InputIterator2 __last2, _OutputIterator __result)
5565{
5566    return _VSTD::set_symmetric_difference(__first1, __last1, __first2, __last2, __result,
5567                                          __less<typename iterator_traits<_InputIterator1>::value_type,
5568                                                 typename iterator_traits<_InputIterator2>::value_type>());
5569}
5570
5571// lexicographical_compare
5572
5573template <class _Compare, class _InputIterator1, class _InputIterator2>
5574_LIBCPP_CONSTEXPR_AFTER_CXX17 bool
5575__lexicographical_compare(_InputIterator1 __first1, _InputIterator1 __last1,
5576                          _InputIterator2 __first2, _InputIterator2 __last2, _Compare __comp)
5577{
5578    for (; __first2 != __last2; ++__first1, (void) ++__first2)
5579    {
5580        if (__first1 == __last1 || __comp(*__first1, *__first2))
5581            return true;
5582        if (__comp(*__first2, *__first1))
5583            return false;
5584    }
5585    return false;
5586}
5587
5588template <class _InputIterator1, class _InputIterator2, class _Compare>
5589_LIBCPP_NODISCARD_EXT inline
5590_LIBCPP_INLINE_VISIBILITY _LIBCPP_CONSTEXPR_AFTER_CXX17
5591bool
5592lexicographical_compare(_InputIterator1 __first1, _InputIterator1 __last1,
5593                        _InputIterator2 __first2, _InputIterator2 __last2, _Compare __comp)
5594{
5595    typedef typename __comp_ref_type<_Compare>::type _Comp_ref;
5596    return __lexicographical_compare<_Comp_ref>(__first1, __last1, __first2, __last2, __comp);
5597}
5598
5599template <class _InputIterator1, class _InputIterator2>
5600_LIBCPP_NODISCARD_EXT inline
5601_LIBCPP_INLINE_VISIBILITY _LIBCPP_CONSTEXPR_AFTER_CXX17
5602bool
5603lexicographical_compare(_InputIterator1 __first1, _InputIterator1 __last1,
5604                        _InputIterator2 __first2, _InputIterator2 __last2)
5605{
5606    return _VSTD::lexicographical_compare(__first1, __last1, __first2, __last2,
5607                                         __less<typename iterator_traits<_InputIterator1>::value_type,
5608                                                typename iterator_traits<_InputIterator2>::value_type>());
5609}
5610
5611// next_permutation
5612
5613template <class _Compare, class _BidirectionalIterator>
5614bool
5615__next_permutation(_BidirectionalIterator __first, _BidirectionalIterator __last, _Compare __comp)
5616{
5617    _BidirectionalIterator __i = __last;
5618    if (__first == __last || __first == --__i)
5619        return false;
5620    while (true)
5621    {
5622        _BidirectionalIterator __ip1 = __i;
5623        if (__comp(*--__i, *__ip1))
5624        {
5625            _BidirectionalIterator __j = __last;
5626            while (!__comp(*__i, *--__j))
5627                ;
5628            swap(*__i, *__j);
5629            _VSTD::reverse(__ip1, __last);
5630            return true;
5631        }
5632        if (__i == __first)
5633        {
5634            _VSTD::reverse(__first, __last);
5635            return false;
5636        }
5637    }
5638}
5639
5640template <class _BidirectionalIterator, class _Compare>
5641inline _LIBCPP_INLINE_VISIBILITY
5642bool
5643next_permutation(_BidirectionalIterator __first, _BidirectionalIterator __last, _Compare __comp)
5644{
5645    typedef typename __comp_ref_type<_Compare>::type _Comp_ref;
5646    return __next_permutation<_Comp_ref>(__first, __last, __comp);
5647}
5648
5649template <class _BidirectionalIterator>
5650inline _LIBCPP_INLINE_VISIBILITY
5651bool
5652next_permutation(_BidirectionalIterator __first, _BidirectionalIterator __last)
5653{
5654    return _VSTD::next_permutation(__first, __last,
5655                                  __less<typename iterator_traits<_BidirectionalIterator>::value_type>());
5656}
5657
5658// prev_permutation
5659
5660template <class _Compare, class _BidirectionalIterator>
5661bool
5662__prev_permutation(_BidirectionalIterator __first, _BidirectionalIterator __last, _Compare __comp)
5663{
5664    _BidirectionalIterator __i = __last;
5665    if (__first == __last || __first == --__i)
5666        return false;
5667    while (true)
5668    {
5669        _BidirectionalIterator __ip1 = __i;
5670        if (__comp(*__ip1, *--__i))
5671        {
5672            _BidirectionalIterator __j = __last;
5673            while (!__comp(*--__j, *__i))
5674                ;
5675            swap(*__i, *__j);
5676            _VSTD::reverse(__ip1, __last);
5677            return true;
5678        }
5679        if (__i == __first)
5680        {
5681            _VSTD::reverse(__first, __last);
5682            return false;
5683        }
5684    }
5685}
5686
5687template <class _BidirectionalIterator, class _Compare>
5688inline _LIBCPP_INLINE_VISIBILITY
5689bool
5690prev_permutation(_BidirectionalIterator __first, _BidirectionalIterator __last, _Compare __comp)
5691{
5692    typedef typename __comp_ref_type<_Compare>::type _Comp_ref;
5693    return __prev_permutation<_Comp_ref>(__first, __last, __comp);
5694}
5695
5696template <class _BidirectionalIterator>
5697inline _LIBCPP_INLINE_VISIBILITY
5698bool
5699prev_permutation(_BidirectionalIterator __first, _BidirectionalIterator __last)
5700{
5701    return _VSTD::prev_permutation(__first, __last,
5702                                  __less<typename iterator_traits<_BidirectionalIterator>::value_type>());
5703}
5704
5705_LIBCPP_END_NAMESPACE_STD
5706
5707_LIBCPP_POP_MACROS
5708
5709#if defined(_LIBCPP_HAS_PARALLEL_ALGORITHMS) && _LIBCPP_STD_VER >= 17
5710#   include <__pstl_algorithm>
5711#endif
5712
5713#endif  // _LIBCPP_ALGORITHM
5714