v1/__algorithm/prev_permutation.h

0001 //===----------------------------------------------------------------------===//
0002 //
0003 // Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
0004 // See https://llvm.org/LICENSE.txt for license information.
0005 // SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
0006 //
0007 //===----------------------------------------------------------------------===//
0008
0009 #ifndef _LIBCPP___ALGORITHM_PREV_PERMUTATION_H
0010 #define _LIBCPP___ALGORITHM_PREV_PERMUTATION_H
0011
0012 #include <__algorithm/comp.h>
0013 #include <__algorithm/comp_ref_type.h>
0014 #include <__algorithm/iterator_operations.h>
0015 #include <__algorithm/reverse.h>
0016 #include <__config>
0017 #include <__iterator/iterator_traits.h>
0018 #include <__utility/move.h>
0019 #include <__utility/pair.h>
0020
0021 #if !defined(_LIBCPP_HAS_NO_PRAGMA_SYSTEM_HEADER)
0022 #  pragma GCC system_header
0023 #endif
0024
0025 _LIBCPP_PUSH_MACROS
0026 #include <__undef_macros>
0027
0028 _LIBCPP_BEGIN_NAMESPACE_STD
0029
0030 template <class _AlgPolicy, class _Compare, class _BidirectionalIterator, class _Sentinel>
0031 _LIBCPP_HIDE_FROM_ABI _LIBCPP_CONSTEXPR_SINCE_CXX20 pair<_BidirectionalIterator, bool>
0032 __prev_permutation(_BidirectionalIterator __first, _Sentinel __last, _Compare&& __comp) {
0033   using _Result = pair<_BidirectionalIterator, bool>;
0034
0035   _BidirectionalIterator __last_iter = _IterOps<_AlgPolicy>::next(__first, __last);
0036   _BidirectionalIterator __i         = __last_iter;
0037   if (__first == __last || __first == --__i)
0038     return _Result(std::move(__last_iter), false);
0039
0040   while (true) {
0041     _BidirectionalIterator __ip1 = __i;
0042     if (__comp(*__ip1, *--__i)) {
0043       _BidirectionalIterator __j = __last_iter;
0044       while (!__comp(*--__j, *__i))
0045         ;
0046       _IterOps<_AlgPolicy>::iter_swap(__i, __j);
0047       std::__reverse<_AlgPolicy>(__ip1, __last_iter);
0048       return _Result(std::move(__last_iter), true);
0049     }
0050     if (__i == __first) {
0051       std::__reverse<_AlgPolicy>(__first, __last_iter);
0052       return _Result(std::move(__last_iter), false);
0053     }
0054   }
0055 }
0056
0057 template <class _BidirectionalIterator, class _Compare>
0058 inline _LIBCPP_HIDE_FROM_ABI _LIBCPP_CONSTEXPR_SINCE_CXX20 bool
0059 prev_permutation(_BidirectionalIterator __first, _BidirectionalIterator __last, _Compare __comp) {
0060   return std::__prev_permutation<_ClassicAlgPolicy>(
0061              std::move(__first), std::move(__last), static_cast<__comp_ref_type<_Compare> >(__comp))
0062       .second;
0063 }
0064
0065 template <class _BidirectionalIterator>
0066 inline _LIBCPP_HIDE_FROM_ABI _LIBCPP_CONSTEXPR_SINCE_CXX20 bool
0067 prev_permutation(_BidirectionalIterator __first, _BidirectionalIterator __last) {
0068   return std::prev_permutation(__first, __last, __less<>());
0069 }
0070
0071 _LIBCPP_END_NAMESPACE_STD
0072
0073 _LIBCPP_POP_MACROS
0074
0075 #endif // _LIBCPP___ALGORITHM_PREV_PERMUTATION_H