libcxx/include/__algorithm/partial_sort.h

   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_PARTIAL_SORT_H
  10 #define _LIBCPP___ALGORITHM_PARTIAL_SORT_H
  11
  12 #include <__algorithm/comp.h>
  13 #include <__algorithm/comp_ref_type.h>
  14 #include <__algorithm/iterator_operations.h>
  15 #include <__algorithm/make_heap.h>
  16 #include <__algorithm/sift_down.h>
  17 #include <__algorithm/sort_heap.h>
  18 #include <__config>
  19 #include <__debug_utils/randomize_range.h>
  20 #include <__iterator/iterator_traits.h>
  21 #include <__type_traits/is_assignable.h>
  22 #include <__type_traits/is_constructible.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 _AlgPolicy, class _Compare, class _RandomAccessIterator, class _Sentinel>
  35 _LIBCPP_HIDE_FROM_ABI _LIBCPP_CONSTEXPR_SINCE_CXX20 _RandomAccessIterator __partial_sort_impl(
  36     _RandomAccessIterator __first, _RandomAccessIterator __middle, _Sentinel __last, _Compare&& __comp) {
  37   if (__first == __middle) {
  38     return _IterOps<_AlgPolicy>::next(__middle, __last);
  39   }
  40
  41   std::__make_heap<_AlgPolicy>(__first, __middle, __comp);
  42
  43   typename iterator_traits<_RandomAccessIterator>::difference_type __len = __middle - __first;
  44   _RandomAccessIterator __i                                              = __middle;
  45   for (; __i != __last; ++__i) {
  46     if (__comp(*__i, *__first)) {
  47       _IterOps<_AlgPolicy>::iter_swap(__i, __first);
  48       std::__sift_down<_AlgPolicy>(__first, __comp, __len, __first);
  49     }
  50   }
  51   std::__sort_heap<_AlgPolicy>(std::move(__first), std::move(__middle), __comp);
  52
  53   return __i;
  54 }
  55
  56 template <class _AlgPolicy, class _Compare, class _RandomAccessIterator, class _Sentinel>
  57 _LIBCPP_HIDE_FROM_ABI _LIBCPP_CONSTEXPR_SINCE_CXX20 _RandomAccessIterator
  58 __partial_sort(_RandomAccessIterator __first, _RandomAccessIterator __middle, _Sentinel __last, _Compare& __comp) {
  59   if (__first == __middle)
  60     return _IterOps<_AlgPolicy>::next(__middle, __last);
  61
  62   std::__debug_randomize_range<_AlgPolicy>(__first, __last);
  63
  64   auto __last_iter =
  65       std::__partial_sort_impl<_AlgPolicy>(__first, __middle, __last, static_cast<__comp_ref_type<_Compare> >(__comp));
  66
  67   std::__debug_randomize_range<_AlgPolicy>(__middle, __last);
  68
  69   return __last_iter;
  70 }
  71
  72 template <class _RandomAccessIterator, class _Compare>
  73 inline _LIBCPP_HIDE_FROM_ABI _LIBCPP_CONSTEXPR_SINCE_CXX20 void partial_sort(
  74     _RandomAccessIterator __first, _RandomAccessIterator __middle, _RandomAccessIterator __last, _Compare __comp) {
  75   static_assert(std::is_copy_constructible<_RandomAccessIterator>::value, "Iterators must be copy constructible.");
  76   static_assert(std::is_copy_assignable<_RandomAccessIterator>::value, "Iterators must be copy assignable.");
  77
  78   (void)std::__partial_sort<_ClassicAlgPolicy>(std::move(__first), std::move(__middle), std::move(__last), __comp);
  79 }
  80
  81 template <class _RandomAccessIterator>
  82 inline _LIBCPP_HIDE_FROM_ABI _LIBCPP_CONSTEXPR_SINCE_CXX20 void
  83 partial_sort(_RandomAccessIterator __first, _RandomAccessIterator __middle, _RandomAccessIterator __last) {
  84   std::partial_sort(__first, __middle, __last, __less<>());
  85 }
  86
  87 _LIBCPP_END_NAMESPACE_STD
  88
  89 _LIBCPP_POP_MACROS
  90
  91 #endif // _LIBCPP___ALGORITHM_PARTIAL_SORT_H