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
34template <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
56template <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
72template <class _RandomAccessIterator, class _Compare>
73inline _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
81template <class _RandomAccessIterator>
82inline _LIBCPP_HIDE_FROM_ABI _LIBCPP_CONSTEXPR_SINCE_CXX20 void
83partial_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