1 //===----------------------------------------------------------------------===// 2 // 3 // Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions. 4 // See https://llvm.org/LICENSE.txt for license information. 5 // SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception 6 // 7 //===----------------------------------------------------------------------===// 8 9 #ifndef _LIBCPP___ALGORITHM_PREV_PERMUTATION_H 10 #define _LIBCPP___ALGORITHM_PREV_PERMUTATION_H 11 12 #include <__algorithm/comp.h> 13 #include <__algorithm/comp_ref_type.h> 14 #include <__algorithm/iterator_operations.h> 15 #include <__algorithm/reverse.h> 16 #include <__config> 17 #include <__iterator/iterator_traits.h> 18 #include <__utility/move.h> 19 #include <__utility/pair.h> 20 21 #if !defined(_LIBCPP_HAS_NO_PRAGMA_SYSTEM_HEADER) 22 # pragma GCC system_header 23 #endif 24 25 _LIBCPP_BEGIN_NAMESPACE_STD 26 27 template <class _AlgPolicy, class _Compare, class _BidirectionalIterator, class _Sentinel> 28 _LIBCPP_CONSTEXPR_AFTER_CXX17 29 pair<_BidirectionalIterator, bool> 30 __prev_permutation(_BidirectionalIterator __first, _Sentinel __last, _Compare&& __comp) 31 { 32 using _Result = pair<_BidirectionalIterator, bool>; 33 34 _BidirectionalIterator __last_iter = _IterOps<_AlgPolicy>::next(__first, __last); 35 _BidirectionalIterator __i = __last_iter; 36 if (__first == __last || __first == --__i) 37 return _Result(std::move(__last_iter), false); 38 39 while (true) 40 { 41 _BidirectionalIterator __ip1 = __i; 42 if (__comp(*__ip1, *--__i)) 43 { 44 _BidirectionalIterator __j = __last_iter; 45 while (!__comp(*--__j, *__i)) 46 ; 47 _IterOps<_AlgPolicy>::iter_swap(__i, __j); 48 std::__reverse<_AlgPolicy>(__ip1, __last_iter); 49 return _Result(std::move(__last_iter), true); 50 } 51 if (__i == __first) 52 { 53 std::__reverse<_AlgPolicy>(__first, __last_iter); 54 return _Result(std::move(__last_iter), false); 55 } 56 } 57 } 58 59 template <class _BidirectionalIterator, class _Compare> 60 inline _LIBCPP_INLINE_VISIBILITY _LIBCPP_CONSTEXPR_AFTER_CXX17 61 bool 62 prev_permutation(_BidirectionalIterator __first, _BidirectionalIterator __last, _Compare __comp) 63 { 64 using _Comp_ref = typename __comp_ref_type<_Compare>::type; 65 return std::__prev_permutation<_ClassicAlgPolicy>( 66 std::move(__first), std::move(__last), static_cast<_Comp_ref>(__comp)).second; 67 } 68 69 template <class _BidirectionalIterator> 70 inline _LIBCPP_INLINE_VISIBILITY _LIBCPP_CONSTEXPR_AFTER_CXX17 71 bool 72 prev_permutation(_BidirectionalIterator __first, _BidirectionalIterator __last) 73 { 74 return _VSTD::prev_permutation(__first, __last, 75 __less<typename iterator_traits<_BidirectionalIterator>::value_type>()); 76 } 77 78 _LIBCPP_END_NAMESPACE_STD 79 80 #endif // _LIBCPP___ALGORITHM_PREV_PERMUTATION_H 81