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/reverse.h> 15 #include <__config> 16 #include <__iterator/iterator_traits.h> 17 #include <__utility/swap.h> 18 19 #if !defined(_LIBCPP_HAS_NO_PRAGMA_SYSTEM_HEADER) 20 # pragma GCC system_header 21 # pragma clang include_instead(<algorithm>) 22 #endif 23 24 _LIBCPP_BEGIN_NAMESPACE_STD 25 26 template <class _Compare, class _BidirectionalIterator> 27 _LIBCPP_CONSTEXPR_AFTER_CXX17 bool 28 __prev_permutation(_BidirectionalIterator __first, _BidirectionalIterator __last, _Compare __comp) 29 { 30 _BidirectionalIterator __i = __last; 31 if (__first == __last || __first == --__i) 32 return false; 33 while (true) 34 { 35 _BidirectionalIterator __ip1 = __i; 36 if (__comp(*__ip1, *--__i)) 37 { 38 _BidirectionalIterator __j = __last; 39 while (!__comp(*--__j, *__i)) 40 ; 41 swap(*__i, *__j); 42 _VSTD::reverse(__ip1, __last); 43 return true; 44 } 45 if (__i == __first) 46 { 47 _VSTD::reverse(__first, __last); 48 return false; 49 } 50 } 51 } 52 53 template <class _BidirectionalIterator, class _Compare> 54 inline _LIBCPP_INLINE_VISIBILITY _LIBCPP_CONSTEXPR_AFTER_CXX17 55 bool 56 prev_permutation(_BidirectionalIterator __first, _BidirectionalIterator __last, _Compare __comp) 57 { 58 typedef typename __comp_ref_type<_Compare>::type _Comp_ref; 59 return _VSTD::__prev_permutation<_Comp_ref>(__first, __last, __comp); 60 } 61 62 template <class _BidirectionalIterator> 63 inline _LIBCPP_INLINE_VISIBILITY _LIBCPP_CONSTEXPR_AFTER_CXX17 64 bool 65 prev_permutation(_BidirectionalIterator __first, _BidirectionalIterator __last) 66 { 67 return _VSTD::prev_permutation(__first, __last, 68 __less<typename iterator_traits<_BidirectionalIterator>::value_type>()); 69 } 70 71 _LIBCPP_END_NAMESPACE_STD 72 73 #endif // _LIBCPP___ALGORITHM_PREV_PERMUTATION_H 74