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_HIDE_FROM_ABI _LIBCPP_CONSTEXPR_SINCE_CXX20 pair<_BidirectionalIterator, bool> 29 __prev_permutation(_BidirectionalIterator __first, _Sentinel __last, _Compare&& __comp) { 30 using _Result = pair<_BidirectionalIterator, bool>; 31 32 _BidirectionalIterator __last_iter = _IterOps<_AlgPolicy>::next(__first, __last); 33 _BidirectionalIterator __i = __last_iter; 34 if (__first == __last || __first == --__i) 35 return _Result(std::move(__last_iter), false); 36 37 while (true) { 38 _BidirectionalIterator __ip1 = __i; 39 if (__comp(*__ip1, *--__i)) { 40 _BidirectionalIterator __j = __last_iter; 41 while (!__comp(*--__j, *__i)) 42 ; 43 _IterOps<_AlgPolicy>::iter_swap(__i, __j); 44 std::__reverse<_AlgPolicy>(__ip1, __last_iter); 45 return _Result(std::move(__last_iter), true); 46 } 47 if (__i == __first) { 48 std::__reverse<_AlgPolicy>(__first, __last_iter); 49 return _Result(std::move(__last_iter), false); 50 } 51 } 52 } 53 54 template <class _BidirectionalIterator, class _Compare> 55 inline _LIBCPP_HIDE_FROM_ABI _LIBCPP_CONSTEXPR_SINCE_CXX20 bool 56 prev_permutation(_BidirectionalIterator __first, _BidirectionalIterator __last, _Compare __comp) { 57 return std::__prev_permutation<_ClassicAlgPolicy>( 58 std::move(__first), std::move(__last), static_cast<__comp_ref_type<_Compare> >(__comp)) 59 .second; 60 } 61 62 template <class _BidirectionalIterator> 63 inline _LIBCPP_HIDE_FROM_ABI _LIBCPP_CONSTEXPR_SINCE_CXX20 bool 64 prev_permutation(_BidirectionalIterator __first, _BidirectionalIterator __last) { 65 return std::prev_permutation(__first, __last, __less<>()); 66 } 67 68 _LIBCPP_END_NAMESPACE_STD 69 70 #endif // _LIBCPP___ALGORITHM_PREV_PERMUTATION_H 71