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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-exception6//7//===----------------------------------------------------------------------===//8 9#ifndef _LIBCPP___ALGORITHM_SAMPLE_H10#define _LIBCPP___ALGORITHM_SAMPLE_H11 12#include <__algorithm/iterator_operations.h>13#include <__algorithm/min.h>14#include <__assert>15#include <__config>16#include <__iterator/distance.h>17#include <__iterator/iterator_traits.h>18#include <__random/uniform_int_distribution.h>19#include <__type_traits/common_type.h>20#include <__utility/move.h>21 22#if !defined(_LIBCPP_HAS_NO_PRAGMA_SYSTEM_HEADER)23# pragma GCC system_header24#endif25 26_LIBCPP_PUSH_MACROS27#include <__undef_macros>28 29_LIBCPP_BEGIN_NAMESPACE_STD30 31template <class _AlgPolicy,32 class _PopulationIterator,33 class _PopulationSentinel,34 class _SampleIterator,35 class _Distance,36 class _UniformRandomNumberGenerator>37_LIBCPP_HIDE_FROM_ABI _SampleIterator __sample(38 _PopulationIterator __first,39 _PopulationSentinel __last,40 _SampleIterator __output_iter,41 _Distance __n,42 _UniformRandomNumberGenerator& __g,43 input_iterator_tag) {44 _Distance __k = 0;45 for (; __first != __last && __k < __n; ++__first, (void)++__k)46 __output_iter[__k] = *__first;47 _Distance __sz = __k;48 for (; __first != __last; ++__first, (void)++__k) {49 _Distance __r = uniform_int_distribution<_Distance>(0, __k)(__g);50 if (__r < __sz)51 __output_iter[__r] = *__first;52 }53 return __output_iter + std::min(__n, __k);54}55 56template <class _AlgPolicy,57 class _PopulationIterator,58 class _PopulationSentinel,59 class _SampleIterator,60 class _Distance,61 class _UniformRandomNumberGenerator>62_LIBCPP_HIDE_FROM_ABI _SampleIterator __sample(63 _PopulationIterator __first,64 _PopulationSentinel __last,65 _SampleIterator __output_iter,66 _Distance __n,67 _UniformRandomNumberGenerator& __g,68 forward_iterator_tag) {69 _Distance __unsampled_sz = _IterOps<_AlgPolicy>::distance(__first, __last);70 for (__n = std::min(__n, __unsampled_sz); __n != 0; ++__first) {71 _Distance __r = uniform_int_distribution<_Distance>(0, --__unsampled_sz)(__g);72 if (__r < __n) {73 *__output_iter++ = *__first;74 --__n;75 }76 }77 return __output_iter;78}79 80template <class _AlgPolicy,81 class _PopulationIterator,82 class _PopulationSentinel,83 class _SampleIterator,84 class _Distance,85 class _UniformRandomNumberGenerator>86_LIBCPP_HIDE_FROM_ABI _SampleIterator __sample(87 _PopulationIterator __first,88 _PopulationSentinel __last,89 _SampleIterator __output_iter,90 _Distance __n,91 _UniformRandomNumberGenerator& __g) {92 _LIBCPP_ASSERT_VALID_ELEMENT_ACCESS(__n >= 0, "N must be a positive number.");93 94 using _PopIterCategory = typename _IterOps<_AlgPolicy>::template __iterator_category<_PopulationIterator>;95 using _Difference = typename _IterOps<_AlgPolicy>::template __difference_type<_PopulationIterator>;96 using _CommonType = typename common_type<_Distance, _Difference>::type;97 98 return std::__sample<_AlgPolicy>(99 std::move(__first), std::move(__last), std::move(__output_iter), _CommonType(__n), __g, _PopIterCategory());100}101 102#if _LIBCPP_STD_VER >= 17103template <class _PopulationIterator, class _SampleIterator, class _Distance, class _UniformRandomNumberGenerator>104inline _LIBCPP_HIDE_FROM_ABI _SampleIterator105sample(_PopulationIterator __first,106 _PopulationIterator __last,107 _SampleIterator __output_iter,108 _Distance __n,109 _UniformRandomNumberGenerator&& __g) {110 static_assert(__has_forward_iterator_category<_PopulationIterator>::value ||111 __has_random_access_iterator_category<_SampleIterator>::value,112 "SampleIterator must meet the requirements of RandomAccessIterator");113 114 return std::__sample<_ClassicAlgPolicy>(std::move(__first), std::move(__last), std::move(__output_iter), __n, __g);115}116 117#endif // _LIBCPP_STD_VER >= 17118 119_LIBCPP_END_NAMESPACE_STD120 121_LIBCPP_POP_MACROS122 123#endif // _LIBCPP___ALGORITHM_SAMPLE_H124