xref: /freebsd/contrib/llvm-project/libcxx/include/__algorithm/is_permutation.h (revision f5f40dd63bc7acbb5312b26ac1ea1103c12352a6)
1 // -*- C++ -*-
2 //===----------------------------------------------------------------------===//
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_IS_PERMUTATION_H
11 #define _LIBCPP___ALGORITHM_IS_PERMUTATION_H
12 
13 #include <__algorithm/comp.h>
14 #include <__algorithm/iterator_operations.h>
15 #include <__config>
16 #include <__functional/identity.h>
17 #include <__functional/invoke.h>
18 #include <__iterator/concepts.h>
19 #include <__iterator/distance.h>
20 #include <__iterator/iterator_traits.h>
21 #include <__iterator/next.h>
22 #include <__type_traits/is_callable.h>
23 #include <__utility/move.h>
24 
25 #if !defined(_LIBCPP_HAS_NO_PRAGMA_SYSTEM_HEADER)
26 #  pragma GCC system_header
27 #endif
28 
29 _LIBCPP_PUSH_MACROS
30 #include <__undef_macros>
31 
32 _LIBCPP_BEGIN_NAMESPACE_STD
33 
34 template <class _Iter1, class _Sent1, class _Iter2, class _Sent2, class = void>
35 struct _ConstTimeDistance : false_type {};
36 
37 #if _LIBCPP_STD_VER >= 20
38 
39 template <class _Iter1, class _Sent1, class _Iter2, class _Sent2>
40 struct _ConstTimeDistance<_Iter1,
41                           _Sent1,
42                           _Iter2,
43                           _Sent2,
44                           __enable_if_t< sized_sentinel_for<_Sent1, _Iter1> && sized_sentinel_for<_Sent2, _Iter2> >>
45     : true_type {};
46 
47 #else
48 
49 template <class _Iter1, class _Iter2>
50 struct _ConstTimeDistance<
51     _Iter1,
52     _Iter1,
53     _Iter2,
54     _Iter2,
55     __enable_if_t< is_same<typename iterator_traits<_Iter1>::iterator_category, random_access_iterator_tag>::value &&
56                    is_same<typename iterator_traits<_Iter2>::iterator_category, random_access_iterator_tag>::value > >
57     : true_type {};
58 
59 #endif // _LIBCPP_STD_VER >= 20
60 
61 // Internal functions
62 
63 // For each element in [f1, l1) see if there are the same number of equal elements in [f2, l2)
64 template <class _AlgPolicy,
65           class _Iter1,
66           class _Sent1,
67           class _Iter2,
68           class _Sent2,
69           class _Proj1,
70           class _Proj2,
71           class _Pred>
72 _LIBCPP_HIDE_FROM_ABI _LIBCPP_CONSTEXPR_SINCE_CXX20 bool __is_permutation_impl(
73     _Iter1 __first1,
74     _Sent1 __last1,
75     _Iter2 __first2,
76     _Sent2 __last2,
77     _Pred&& __pred,
78     _Proj1&& __proj1,
79     _Proj2&& __proj2) {
80   using _D1 = __iter_diff_t<_Iter1>;
81 
82   for (auto __i = __first1; __i != __last1; ++__i) {
83     //  Have we already counted the number of *__i in [f1, l1)?
84     auto __match = __first1;
85     for (; __match != __i; ++__match) {
86       if (std::__invoke(__pred, std::__invoke(__proj1, *__match), std::__invoke(__proj1, *__i)))
87         break;
88     }
89 
90     if (__match == __i) {
91       // Count number of *__i in [f2, l2)
92       _D1 __c2 = 0;
93       for (auto __j = __first2; __j != __last2; ++__j) {
94         if (std::__invoke(__pred, std::__invoke(__proj1, *__i), std::__invoke(__proj2, *__j)))
95           ++__c2;
96       }
97       if (__c2 == 0)
98         return false;
99 
100       // Count number of *__i in [__i, l1) (we can start with 1)
101       _D1 __c1 = 1;
102       for (auto __j = _IterOps<_AlgPolicy>::next(__i); __j != __last1; ++__j) {
103         if (std::__invoke(__pred, std::__invoke(__proj1, *__i), std::__invoke(__proj1, *__j)))
104           ++__c1;
105       }
106       if (__c1 != __c2)
107         return false;
108     }
109   }
110 
111   return true;
112 }
113 
114 // 2+1 iterators, predicate. Not used by range algorithms.
115 template <class _AlgPolicy, class _ForwardIterator1, class _Sentinel1, class _ForwardIterator2, class _BinaryPredicate>
116 _LIBCPP_NODISCARD_EXT _LIBCPP_HIDE_FROM_ABI _LIBCPP_CONSTEXPR_SINCE_CXX20 bool __is_permutation(
117     _ForwardIterator1 __first1, _Sentinel1 __last1, _ForwardIterator2 __first2, _BinaryPredicate&& __pred) {
118   // Shorten sequences as much as possible by lopping of any equal prefix.
119   for (; __first1 != __last1; ++__first1, (void)++__first2) {
120     if (!__pred(*__first1, *__first2))
121       break;
122   }
123 
124   if (__first1 == __last1)
125     return true;
126 
127   //  __first1 != __last1 && *__first1 != *__first2
128   using _D1 = __iter_diff_t<_ForwardIterator1>;
129   _D1 __l1  = _IterOps<_AlgPolicy>::distance(__first1, __last1);
130   if (__l1 == _D1(1))
131     return false;
132   auto __last2 = _IterOps<_AlgPolicy>::next(__first2, __l1);
133 
134   return std::__is_permutation_impl<_AlgPolicy>(
135       std::move(__first1),
136       std::move(__last1),
137       std::move(__first2),
138       std::move(__last2),
139       __pred,
140       __identity(),
141       __identity());
142 }
143 
144 // 2+2 iterators, predicate, non-constant time `distance`.
145 template <class _AlgPolicy,
146           class _Iter1,
147           class _Sent1,
148           class _Iter2,
149           class _Sent2,
150           class _Proj1,
151           class _Proj2,
152           class _Pred>
153 _LIBCPP_HIDE_FROM_ABI _LIBCPP_CONSTEXPR_SINCE_CXX20 bool __is_permutation(
154     _Iter1 __first1,
155     _Sent1 __last1,
156     _Iter2 __first2,
157     _Sent2 __last2,
158     _Pred&& __pred,
159     _Proj1&& __proj1,
160     _Proj2&& __proj2,
161     /*_ConstTimeDistance=*/false_type) {
162   // Shorten sequences as much as possible by lopping of any equal prefix.
163   while (__first1 != __last1 && __first2 != __last2) {
164     if (!std::__invoke(__pred, std::__invoke(__proj1, *__first1), std::__invoke(__proj2, *__first2)))
165       break;
166     ++__first1;
167     ++__first2;
168   }
169 
170   if (__first1 == __last1)
171     return __first2 == __last2;
172   if (__first2 == __last2) // Second range is shorter
173     return false;
174 
175   using _D1 = __iter_diff_t<_Iter1>;
176   _D1 __l1  = _IterOps<_AlgPolicy>::distance(__first1, __last1);
177 
178   using _D2 = __iter_diff_t<_Iter2>;
179   _D2 __l2  = _IterOps<_AlgPolicy>::distance(__first2, __last2);
180   if (__l1 != __l2)
181     return false;
182 
183   return std::__is_permutation_impl<_AlgPolicy>(
184       std::move(__first1), std::move(__last1), std::move(__first2), std::move(__last2), __pred, __proj1, __proj2);
185 }
186 
187 // 2+2 iterators, predicate, specialization for constant-time `distance` call.
188 template <class _AlgPolicy,
189           class _Iter1,
190           class _Sent1,
191           class _Iter2,
192           class _Sent2,
193           class _Proj1,
194           class _Proj2,
195           class _Pred>
196 _LIBCPP_HIDE_FROM_ABI _LIBCPP_CONSTEXPR_SINCE_CXX20 bool __is_permutation(
197     _Iter1 __first1,
198     _Sent1 __last1,
199     _Iter2 __first2,
200     _Sent2 __last2,
201     _Pred&& __pred,
202     _Proj1&& __proj1,
203     _Proj2&& __proj2,
204     /*_ConstTimeDistance=*/true_type) {
205   if (std::distance(__first1, __last1) != std::distance(__first2, __last2))
206     return false;
207   return std::__is_permutation<_AlgPolicy>(
208       std::move(__first1),
209       std::move(__last1),
210       std::move(__first2),
211       std::move(__last2),
212       __pred,
213       __proj1,
214       __proj2,
215       /*_ConstTimeDistance=*/false_type());
216 }
217 
218 // 2+2 iterators, predicate
219 template <class _AlgPolicy,
220           class _Iter1,
221           class _Sent1,
222           class _Iter2,
223           class _Sent2,
224           class _Proj1,
225           class _Proj2,
226           class _Pred>
227 _LIBCPP_HIDE_FROM_ABI _LIBCPP_CONSTEXPR_SINCE_CXX20 bool __is_permutation(
228     _Iter1 __first1,
229     _Sent1 __last1,
230     _Iter2 __first2,
231     _Sent2 __last2,
232     _Pred&& __pred,
233     _Proj1&& __proj1,
234     _Proj2&& __proj2) {
235   return std::__is_permutation<_AlgPolicy>(
236       std::move(__first1),
237       std::move(__last1),
238       std::move(__first2),
239       std::move(__last2),
240       __pred,
241       __proj1,
242       __proj2,
243       _ConstTimeDistance<_Iter1, _Sent1, _Iter2, _Sent2>());
244 }
245 
246 // Public interface
247 
248 // 2+1 iterators, predicate
249 template <class _ForwardIterator1, class _ForwardIterator2, class _BinaryPredicate>
250 _LIBCPP_NODISCARD_EXT _LIBCPP_HIDE_FROM_ABI _LIBCPP_CONSTEXPR_SINCE_CXX20 bool is_permutation(
251     _ForwardIterator1 __first1, _ForwardIterator1 __last1, _ForwardIterator2 __first2, _BinaryPredicate __pred) {
252   static_assert(__is_callable<_BinaryPredicate, decltype(*__first1), decltype(*__first2)>::value,
253                 "The predicate has to be callable");
254 
255   return std::__is_permutation<_ClassicAlgPolicy>(std::move(__first1), std::move(__last1), std::move(__first2), __pred);
256 }
257 
258 // 2+1 iterators
259 template <class _ForwardIterator1, class _ForwardIterator2>
260 _LIBCPP_NODISCARD_EXT inline _LIBCPP_HIDE_FROM_ABI _LIBCPP_CONSTEXPR_SINCE_CXX20 bool
261 is_permutation(_ForwardIterator1 __first1, _ForwardIterator1 __last1, _ForwardIterator2 __first2) {
262   return std::is_permutation(__first1, __last1, __first2, __equal_to());
263 }
264 
265 #if _LIBCPP_STD_VER >= 14
266 
267 // 2+2 iterators
268 template <class _ForwardIterator1, class _ForwardIterator2>
269 _LIBCPP_NODISCARD_EXT inline _LIBCPP_HIDE_FROM_ABI _LIBCPP_CONSTEXPR_SINCE_CXX20 bool is_permutation(
270     _ForwardIterator1 __first1, _ForwardIterator1 __last1, _ForwardIterator2 __first2, _ForwardIterator2 __last2) {
271   return std::__is_permutation<_ClassicAlgPolicy>(
272       std::move(__first1),
273       std::move(__last1),
274       std::move(__first2),
275       std::move(__last2),
276       __equal_to(),
277       __identity(),
278       __identity());
279 }
280 
281 // 2+2 iterators, predicate
282 template <class _ForwardIterator1, class _ForwardIterator2, class _BinaryPredicate>
283 _LIBCPP_NODISCARD_EXT inline _LIBCPP_HIDE_FROM_ABI _LIBCPP_CONSTEXPR_SINCE_CXX20 bool is_permutation(
284     _ForwardIterator1 __first1,
285     _ForwardIterator1 __last1,
286     _ForwardIterator2 __first2,
287     _ForwardIterator2 __last2,
288     _BinaryPredicate __pred) {
289   static_assert(__is_callable<_BinaryPredicate, decltype(*__first1), decltype(*__first2)>::value,
290                 "The predicate has to be callable");
291 
292   return std::__is_permutation<_ClassicAlgPolicy>(
293       std::move(__first1),
294       std::move(__last1),
295       std::move(__first2),
296       std::move(__last2),
297       __pred,
298       __identity(),
299       __identity());
300 }
301 
302 #endif // _LIBCPP_STD_VER >= 14
303 
304 _LIBCPP_END_NAMESPACE_STD
305 
306 _LIBCPP_POP_MACROS
307 
308 #endif // _LIBCPP___ALGORITHM_IS_PERMUTATION_H
309