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