113 lines
4.3 KiB
C++
113 lines
4.3 KiB
C++
//===----------------------------------------------------------------------===//
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//
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// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
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// See https://llvm.org/LICENSE.txt for license information.
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// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
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//
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//===----------------------------------------------------------------------===//
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#ifndef _LIBCPP___ALGORITHM_SAMPLE_H
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#define _LIBCPP___ALGORITHM_SAMPLE_H
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#include <__algorithm/iterator_operations.h>
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#include <__algorithm/min.h>
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#include <__assert>
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#include <__config>
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#include <__iterator/distance.h>
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#include <__iterator/iterator_traits.h>
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#include <__random/uniform_int_distribution.h>
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#include <__utility/move.h>
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#include <type_traits>
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#if !defined(_LIBCPP_HAS_NO_PRAGMA_SYSTEM_HEADER)
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# pragma GCC system_header
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#endif
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_LIBCPP_PUSH_MACROS
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#include <__undef_macros>
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_LIBCPP_BEGIN_NAMESPACE_STD
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template <class _AlgPolicy,
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class _PopulationIterator, class _PopulationSentinel, class _SampleIterator, class _Distance,
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class _UniformRandomNumberGenerator>
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_LIBCPP_INLINE_VISIBILITY
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_SampleIterator __sample(_PopulationIterator __first,
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_PopulationSentinel __last, _SampleIterator __output_iter,
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_Distance __n,
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_UniformRandomNumberGenerator& __g,
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input_iterator_tag) {
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_Distance __k = 0;
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for (; __first != __last && __k < __n; ++__first, (void) ++__k)
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__output_iter[__k] = *__first;
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_Distance __sz = __k;
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for (; __first != __last; ++__first, (void) ++__k) {
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_Distance __r = uniform_int_distribution<_Distance>(0, __k)(__g);
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if (__r < __sz)
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__output_iter[__r] = *__first;
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}
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return __output_iter + _VSTD::min(__n, __k);
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}
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template <class _AlgPolicy,
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class _PopulationIterator, class _PopulationSentinel, class _SampleIterator, class _Distance,
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class _UniformRandomNumberGenerator>
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_LIBCPP_INLINE_VISIBILITY
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_SampleIterator __sample(_PopulationIterator __first,
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_PopulationSentinel __last, _SampleIterator __output_iter,
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_Distance __n,
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_UniformRandomNumberGenerator& __g,
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forward_iterator_tag) {
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_Distance __unsampled_sz = _IterOps<_AlgPolicy>::distance(__first, __last);
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for (__n = _VSTD::min(__n, __unsampled_sz); __n != 0; ++__first) {
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_Distance __r = uniform_int_distribution<_Distance>(0, --__unsampled_sz)(__g);
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if (__r < __n) {
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*__output_iter++ = *__first;
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--__n;
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}
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}
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return __output_iter;
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}
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template <class _AlgPolicy,
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class _PopulationIterator, class _PopulationSentinel, class _SampleIterator, class _Distance,
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class _UniformRandomNumberGenerator>
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_LIBCPP_INLINE_VISIBILITY
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_SampleIterator __sample(_PopulationIterator __first,
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_PopulationSentinel __last, _SampleIterator __output_iter,
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_Distance __n, _UniformRandomNumberGenerator& __g) {
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_LIBCPP_ASSERT(__n >= 0, "N must be a positive number.");
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using _PopIterCategory = typename _IterOps<_AlgPolicy>::template __iterator_category<_PopulationIterator>;
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using _Difference = typename _IterOps<_AlgPolicy>::template __difference_type<_PopulationIterator>;
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using _CommonType = typename common_type<_Distance, _Difference>::type;
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return std::__sample<_AlgPolicy>(
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std::move(__first), std::move(__last), std::move(__output_iter), _CommonType(__n),
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__g, _PopIterCategory());
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}
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#if _LIBCPP_STD_VER > 14
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template <class _PopulationIterator, class _SampleIterator, class _Distance,
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class _UniformRandomNumberGenerator>
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inline _LIBCPP_INLINE_VISIBILITY
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_SampleIterator sample(_PopulationIterator __first,
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_PopulationIterator __last, _SampleIterator __output_iter,
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_Distance __n, _UniformRandomNumberGenerator&& __g) {
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static_assert(__is_cpp17_forward_iterator<_PopulationIterator>::value ||
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__is_cpp17_random_access_iterator<_SampleIterator>::value,
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"SampleIterator must meet the requirements of RandomAccessIterator");
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return std::__sample<_ClassicAlgPolicy>(
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std::move(__first), std::move(__last), std::move(__output_iter), __n, __g);
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}
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#endif // _LIBCPP_STD_VER > 14
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_LIBCPP_END_NAMESPACE_STD
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_LIBCPP_POP_MACROS
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#endif // _LIBCPP___ALGORITHM_SAMPLE_H
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