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