2 //===----------------------------------------------------------------------===//
4 // Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
5 // See https://llvm.org/LICENSE.txt for license information.
6 // SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
8 //===----------------------------------------------------------------------===//
10 #ifndef _LIBCPP___ALGORITHM_IS_PERMUTATION_H
11 #define _LIBCPP___ALGORITHM_IS_PERMUTATION_H
13 #include <__algorithm/comp.h>
15 #include <__iterator/iterator_traits.h>
16 #include <__iterator/next.h>
17 #include <iterator> // FIXME: replace with <__iterator/distance.h> when it lands
19 #if !defined(_LIBCPP_HAS_NO_PRAGMA_SYSTEM_HEADER)
20 #pragma GCC system_header
24 #include <__undef_macros>
26 _LIBCPP_BEGIN_NAMESPACE_STD
28 template <class _ForwardIterator1, class _ForwardIterator2, class _BinaryPredicate>
29 _LIBCPP_NODISCARD_EXT _LIBCPP_CONSTEXPR_AFTER_CXX17 bool
30 is_permutation(_ForwardIterator1 __first1, _ForwardIterator1 __last1, _ForwardIterator2 __first2,
31 _BinaryPredicate __pred) {
32 // shorten sequences as much as possible by lopping of any equal prefix
33 for (; __first1 != __last1; ++__first1, (void)++__first2)
34 if (!__pred(*__first1, *__first2))
36 if (__first1 == __last1)
39 // __first1 != __last1 && *__first1 != *__first2
40 typedef typename iterator_traits<_ForwardIterator1>::difference_type _D1;
41 _D1 __l1 = _VSTD::distance(__first1, __last1);
44 _ForwardIterator2 __last2 = _VSTD::next(__first2, __l1);
45 // For each element in [f1, l1) see if there are the same number of
46 // equal elements in [f2, l2)
47 for (_ForwardIterator1 __i = __first1; __i != __last1; ++__i) {
48 // Have we already counted the number of *__i in [f1, l1)?
49 _ForwardIterator1 __match = __first1;
50 for (; __match != __i; ++__match)
51 if (__pred(*__match, *__i))
54 // Count number of *__i in [f2, l2)
56 for (_ForwardIterator2 __j = __first2; __j != __last2; ++__j)
57 if (__pred(*__i, *__j))
61 // Count number of *__i in [__i, l1) (we can start with 1)
63 for (_ForwardIterator1 __j = _VSTD::next(__i); __j != __last1; ++__j)
64 if (__pred(*__i, *__j))
73 template <class _ForwardIterator1, class _ForwardIterator2>
74 _LIBCPP_NODISCARD_EXT inline _LIBCPP_INLINE_VISIBILITY _LIBCPP_CONSTEXPR_AFTER_CXX17 bool
75 is_permutation(_ForwardIterator1 __first1, _ForwardIterator1 __last1, _ForwardIterator2 __first2) {
76 typedef typename iterator_traits<_ForwardIterator1>::value_type __v1;
77 typedef typename iterator_traits<_ForwardIterator2>::value_type __v2;
78 return _VSTD::is_permutation(__first1, __last1, __first2, __equal_to<__v1, __v2>());
81 #if _LIBCPP_STD_VER > 11
82 template <class _BinaryPredicate, class _ForwardIterator1, class _ForwardIterator2>
83 _LIBCPP_CONSTEXPR_AFTER_CXX17 bool
84 __is_permutation(_ForwardIterator1 __first1, _ForwardIterator1 __last1, _ForwardIterator2 __first2,
85 _ForwardIterator2 __last2, _BinaryPredicate __pred, forward_iterator_tag, forward_iterator_tag) {
86 // shorten sequences as much as possible by lopping of any equal prefix
87 for (; __first1 != __last1 && __first2 != __last2; ++__first1, (void)++__first2)
88 if (!__pred(*__first1, *__first2))
90 if (__first1 == __last1)
91 return __first2 == __last2;
92 else if (__first2 == __last2)
95 typedef typename iterator_traits<_ForwardIterator1>::difference_type _D1;
96 _D1 __l1 = _VSTD::distance(__first1, __last1);
98 typedef typename iterator_traits<_ForwardIterator2>::difference_type _D2;
99 _D2 __l2 = _VSTD::distance(__first2, __last2);
103 // For each element in [f1, l1) see if there are the same number of
104 // equal elements in [f2, l2)
105 for (_ForwardIterator1 __i = __first1; __i != __last1; ++__i) {
106 // Have we already counted the number of *__i in [f1, l1)?
107 _ForwardIterator1 __match = __first1;
108 for (; __match != __i; ++__match)
109 if (__pred(*__match, *__i))
111 if (__match == __i) {
112 // Count number of *__i in [f2, l2)
114 for (_ForwardIterator2 __j = __first2; __j != __last2; ++__j)
115 if (__pred(*__i, *__j))
119 // Count number of *__i in [__i, l1) (we can start with 1)
121 for (_ForwardIterator1 __j = _VSTD::next(__i); __j != __last1; ++__j)
122 if (__pred(*__i, *__j))
131 template <class _BinaryPredicate, class _RandomAccessIterator1, class _RandomAccessIterator2>
132 _LIBCPP_CONSTEXPR_AFTER_CXX17 bool __is_permutation(_RandomAccessIterator1 __first1, _RandomAccessIterator2 __last1,
133 _RandomAccessIterator1 __first2, _RandomAccessIterator2 __last2,
134 _BinaryPredicate __pred, random_access_iterator_tag,
135 random_access_iterator_tag) {
136 if (_VSTD::distance(__first1, __last1) != _VSTD::distance(__first2, __last2))
138 return _VSTD::is_permutation<_RandomAccessIterator1, _RandomAccessIterator2,
139 typename add_lvalue_reference<_BinaryPredicate>::type>(__first1, __last1, __first2,
143 template <class _ForwardIterator1, class _ForwardIterator2, class _BinaryPredicate>
144 _LIBCPP_NODISCARD_EXT inline _LIBCPP_INLINE_VISIBILITY _LIBCPP_CONSTEXPR_AFTER_CXX17 bool
145 is_permutation(_ForwardIterator1 __first1, _ForwardIterator1 __last1, _ForwardIterator2 __first2,
146 _ForwardIterator2 __last2, _BinaryPredicate __pred) {
147 return _VSTD::__is_permutation<typename add_lvalue_reference<_BinaryPredicate>::type>(
148 __first1, __last1, __first2, __last2, __pred, typename iterator_traits<_ForwardIterator1>::iterator_category(),
149 typename iterator_traits<_ForwardIterator2>::iterator_category());
152 template <class _ForwardIterator1, class _ForwardIterator2>
153 _LIBCPP_NODISCARD_EXT inline _LIBCPP_INLINE_VISIBILITY _LIBCPP_CONSTEXPR_AFTER_CXX17 bool
154 is_permutation(_ForwardIterator1 __first1, _ForwardIterator1 __last1, _ForwardIterator2 __first2,
155 _ForwardIterator2 __last2) {
156 typedef typename iterator_traits<_ForwardIterator1>::value_type __v1;
157 typedef typename iterator_traits<_ForwardIterator2>::value_type __v2;
158 return _VSTD::__is_permutation(__first1, __last1, __first2, __last2, __equal_to<__v1, __v2>(),
159 typename iterator_traits<_ForwardIterator1>::iterator_category(),
160 typename iterator_traits<_ForwardIterator2>::iterator_category());
164 _LIBCPP_END_NAMESPACE_STD
168 #endif // _LIBCPP___ALGORITHM_IS_PERMUTATION_H