libcxx/include/__algorithm/is_permutation.h

   1 // -*- C++ -*-
   2 //===----------------------------------------------------------------------===//
   3 //
   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
   7 //
   8 //===----------------------------------------------------------------------===//
   9
  10 #ifndef _LIBCPP___ALGORITHM_IS_PERMUTATION_H
  11 #define _LIBCPP___ALGORITHM_IS_PERMUTATION_H
  12
  13 #include <__algorithm/comp.h>
  14 #include <__algorithm/iterator_operations.h>
  15 #include <__config>
  16 #include <__functional/identity.h>
  17 #include <__functional/invoke.h>
  18 #include <__iterator/concepts.h>
  19 #include <__iterator/distance.h>
  20 #include <__iterator/iterator_traits.h>
  21 #include <__iterator/next.h>
  22 #include <__type_traits/is_callable.h>
  23 #include <__utility/move.h>
  24
  25 #if !defined(_LIBCPP_HAS_NO_PRAGMA_SYSTEM_HEADER)
  26 #  pragma GCC system_header
  27 #endif
  28
  29 _LIBCPP_PUSH_MACROS
  30 #include <__undef_macros>
  31
  32 _LIBCPP_BEGIN_NAMESPACE_STD
  33
  34 template <class _Iter1, class _Sent1, class _Iter2, class _Sent2, class = void>
  35 struct _ConstTimeDistance : false_type {};
  36
  37 #if _LIBCPP_STD_VER >= 20
  38
  39 template <class _Iter1, class _Sent1, class _Iter2, class _Sent2>
  40 struct _ConstTimeDistance<_Iter1, _Sent1, _Iter2, _Sent2, __enable_if_t<
  41   sized_sentinel_for<_Sent1, _Iter1> &&
  42   sized_sentinel_for<_Sent2, _Iter2>
  43 >> : true_type {};
  44
  45 #else
  46
  47 template <class _Iter1, class _Iter2>
  48 struct _ConstTimeDistance<_Iter1, _Iter1, _Iter2, _Iter2, __enable_if_t<
  49     is_same<typename iterator_traits<_Iter1>::iterator_category, random_access_iterator_tag>::value &&
  50     is_same<typename iterator_traits<_Iter2>::iterator_category, random_access_iterator_tag>::value
  51 > > : true_type {};
  52
  53 #endif // _LIBCPP_STD_VER >= 20
  54
  55 // Internal functions
  56
  57 // For each element in [f1, l1) see if there are the same number of equal elements in [f2, l2)
  58 template <class _AlgPolicy,
  59           class _Iter1, class _Sent1, class _Iter2, class _Sent2,
  60           class _Proj1, class _Proj2, class _Pred>
  61 _LIBCPP_HIDE_FROM_ABI _LIBCPP_CONSTEXPR_SINCE_CXX20 bool
  62 __is_permutation_impl(_Iter1 __first1, _Sent1 __last1, _Iter2 __first2, _Sent2 __last2,
  63                       _Pred&& __pred, _Proj1&& __proj1, _Proj2&& __proj2) {
  64   using _D1 = __iter_diff_t<_Iter1>;
  65
  66   for (auto __i = __first1; __i != __last1; ++__i) {
  67     //  Have we already counted the number of *__i in [f1, l1)?
  68     auto __match = __first1;
  69     for (; __match != __i; ++__match) {
  70       if (std::__invoke(__pred, std::__invoke(__proj1, *__match), std::__invoke(__proj1, *__i)))
  71         break;
  72     }
  73
  74     if (__match == __i) {
  75       // Count number of *__i in [f2, l2)
  76       _D1 __c2 = 0;
  77       for (auto __j = __first2; __j != __last2; ++__j) {
  78         if (std::__invoke(__pred, std::__invoke(__proj1, *__i), std::__invoke(__proj2, *__j)))
  79           ++__c2;
  80       }
  81       if (__c2 == 0)
  82         return false;
  83
  84       // Count number of *__i in [__i, l1) (we can start with 1)
  85       _D1 __c1 = 1;
  86       for (auto __j = _IterOps<_AlgPolicy>::next(__i); __j != __last1; ++__j) {
  87         if (std::__invoke(__pred, std::__invoke(__proj1, *__i), std::__invoke(__proj1, *__j)))
  88           ++__c1;
  89       }
  90       if (__c1 != __c2)
  91         return false;
  92     }
  93   }
  94
  95   return true;
  96 }
  97
  98 // 2+1 iterators, predicate. Not used by range algorithms.
  99 template <class _AlgPolicy, class _ForwardIterator1, class _Sentinel1, class _ForwardIterator2, class _BinaryPredicate>
 100 _LIBCPP_NODISCARD_EXT _LIBCPP_HIDE_FROM_ABI _LIBCPP_CONSTEXPR_SINCE_CXX20 bool
 101 __is_permutation(_ForwardIterator1 __first1, _Sentinel1 __last1, _ForwardIterator2 __first2,
 102                  _BinaryPredicate&& __pred) {
 103   // Shorten sequences as much as possible by lopping of any equal prefix.
 104   for (; __first1 != __last1; ++__first1, (void)++__first2) {
 105     if (!__pred(*__first1, *__first2))
 106       break;
 107   }
 108
 109   if (__first1 == __last1)
 110     return true;
 111
 112   //  __first1 != __last1 && *__first1 != *__first2
 113   using _D1 = __iter_diff_t<_ForwardIterator1>;
 114   _D1 __l1 = _IterOps<_AlgPolicy>::distance(__first1, __last1);
 115   if (__l1 == _D1(1))
 116     return false;
 117   auto __last2 = _IterOps<_AlgPolicy>::next(__first2, __l1);
 118
 119   return std::__is_permutation_impl<_AlgPolicy>(
 120       std::move(__first1), std::move(__last1), std::move(__first2), std::move(__last2),
 121       __pred, __identity(), __identity());
 122 }
 123
 124 // 2+2 iterators, predicate, non-constant time `distance`.
 125 template <class _AlgPolicy,
 126           class _Iter1, class _Sent1, class _Iter2, class _Sent2,
 127           class _Proj1, class _Proj2, class _Pred>
 128 _LIBCPP_HIDE_FROM_ABI _LIBCPP_CONSTEXPR_SINCE_CXX20 bool
 129 __is_permutation(_Iter1 __first1, _Sent1 __last1, _Iter2 __first2, _Sent2 __last2,
 130                  _Pred&& __pred, _Proj1&& __proj1, _Proj2&& __proj2,
 131                  /*_ConstTimeDistance=*/false_type) {
 132   // Shorten sequences as much as possible by lopping of any equal prefix.
 133   while (__first1 != __last1 && __first2 != __last2) {
 134     if (!std::__invoke(__pred, std::__invoke(__proj1, *__first1), std::__invoke(__proj2, *__first2)))
 135       break;
 136     ++__first1;
 137     ++__first2;
 138   }
 139
 140   if (__first1 == __last1)
 141     return __first2 == __last2;
 142   if (__first2 == __last2) // Second range is shorter
 143     return false;
 144
 145   using _D1 = __iter_diff_t<_Iter1>;
 146   _D1 __l1 = _IterOps<_AlgPolicy>::distance(__first1, __last1);
 147
 148   using _D2 = __iter_diff_t<_Iter2>;
 149   _D2 __l2 = _IterOps<_AlgPolicy>::distance(__first2, __last2);
 150   if (__l1 != __l2)
 151     return false;
 152
 153   return std::__is_permutation_impl<_AlgPolicy>(
 154       std::move(__first1), std::move(__last1), std::move(__first2), std::move(__last2),
 155       __pred, __proj1, __proj2);
 156 }
 157
 158 // 2+2 iterators, predicate, specialization for constant-time `distance` call.
 159 template <class _AlgPolicy,
 160           class _Iter1, class _Sent1, class _Iter2, class _Sent2,
 161           class _Proj1, class _Proj2, class _Pred>
 162 _LIBCPP_HIDE_FROM_ABI _LIBCPP_CONSTEXPR_SINCE_CXX20 bool
 163 __is_permutation(_Iter1 __first1, _Sent1 __last1, _Iter2 __first2, _Sent2 __last2,
 164                  _Pred&& __pred, _Proj1&& __proj1, _Proj2&& __proj2,
 165                  /*_ConstTimeDistance=*/true_type) {
 166   if (std::distance(__first1, __last1) != std::distance(__first2, __last2))
 167     return false;
 168   return std::__is_permutation<_AlgPolicy>(
 169       std::move(__first1), std::move(__last1), std::move(__first2), std::move(__last2),
 170       __pred, __proj1, __proj2,
 171       /*_ConstTimeDistance=*/false_type());
 172 }
 173
 174 // 2+2 iterators, predicate
 175 template <class _AlgPolicy,
 176           class _Iter1, class _Sent1, class _Iter2, class _Sent2,
 177           class _Proj1, class _Proj2, class _Pred>
 178 _LIBCPP_HIDE_FROM_ABI _LIBCPP_CONSTEXPR_SINCE_CXX20 bool
 179 __is_permutation(_Iter1 __first1, _Sent1 __last1, _Iter2 __first2, _Sent2 __last2,
 180                  _Pred&& __pred, _Proj1&& __proj1, _Proj2&& __proj2) {
 181   return std::__is_permutation<_AlgPolicy>(
 182       std::move(__first1), std::move(__last1), std::move(__first2), std::move(__last2),
 183       __pred, __proj1, __proj2,
 184       _ConstTimeDistance<_Iter1, _Sent1, _Iter2, _Sent2>());
 185 }
 186
 187 // Public interface
 188
 189 // 2+1 iterators, predicate
 190 template <class _ForwardIterator1, class _ForwardIterator2, class _BinaryPredicate>
 191 _LIBCPP_NODISCARD_EXT _LIBCPP_HIDE_FROM_ABI _LIBCPP_CONSTEXPR_SINCE_CXX20 bool
 192 is_permutation(_ForwardIterator1 __first1, _ForwardIterator1 __last1, _ForwardIterator2 __first2,
 193                _BinaryPredicate __pred) {
 194   static_assert(__is_callable<_BinaryPredicate, decltype(*__first1), decltype(*__first2)>::value,
 195       "The predicate has to be callable");
 196
 197   return std::__is_permutation<_ClassicAlgPolicy>(
 198       std::move(__first1), std::move(__last1), std::move(__first2), __pred);
 199 }
 200
 201 // 2+1 iterators
 202 template <class _ForwardIterator1, class _ForwardIterator2>
 203 _LIBCPP_NODISCARD_EXT inline _LIBCPP_HIDE_FROM_ABI _LIBCPP_CONSTEXPR_SINCE_CXX20 bool
 204 is_permutation(_ForwardIterator1 __first1, _ForwardIterator1 __last1, _ForwardIterator2 __first2) {
 205   return std::is_permutation(__first1, __last1, __first2, __equal_to());
 206 }
 207
 208 #if _LIBCPP_STD_VER >= 14
 209
 210 // 2+2 iterators
 211 template <class _ForwardIterator1, class _ForwardIterator2>
 212 _LIBCPP_NODISCARD_EXT inline _LIBCPP_HIDE_FROM_ABI _LIBCPP_CONSTEXPR_SINCE_CXX20 bool is_permutation(
 213     _ForwardIterator1 __first1, _ForwardIterator1 __last1, _ForwardIterator2 __first2, _ForwardIterator2 __last2) {
 214   return std::__is_permutation<_ClassicAlgPolicy>(
 215       std::move(__first1),
 216       std::move(__last1),
 217       std::move(__first2),
 218       std::move(__last2),
 219       __equal_to(),
 220       __identity(),
 221       __identity());
 222 }
 223
 224 // 2+2 iterators, predicate
 225 template <class _ForwardIterator1, class _ForwardIterator2, class _BinaryPredicate>
 226 _LIBCPP_NODISCARD_EXT inline _LIBCPP_HIDE_FROM_ABI _LIBCPP_CONSTEXPR_SINCE_CXX20 bool
 227 is_permutation(_ForwardIterator1 __first1, _ForwardIterator1 __last1, _ForwardIterator2 __first2,
 228                _ForwardIterator2 __last2, _BinaryPredicate __pred) {
 229   static_assert(__is_callable<_BinaryPredicate, decltype(*__first1), decltype(*__first2)>::value,
 230       "The predicate has to be callable");
 231
 232   return std::__is_permutation<_ClassicAlgPolicy>(
 233       std::move(__first1), std::move(__last1), std::move(__first2), std::move(__last2),
 234       __pred, __identity(), __identity());
 235 }
 236
 237 #endif // _LIBCPP_STD_VER >= 14
 238
 239 _LIBCPP_END_NAMESPACE_STD
 240
 241 _LIBCPP_POP_MACROS
 242
 243 #endif // _LIBCPP___ALGORITHM_IS_PERMUTATION_H