libstdc++
experimental/algorithm
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1// <experimental/algorithm> -*- C++ -*-
2
3// Copyright (C) 2014-2016 Free Software Foundation, Inc.
4//
5// This file is part of the GNU ISO C++ Library. This library is free
6// software; you can redistribute it and/or modify it under the
7// terms of the GNU General Public License as published by the
8// Free Software Foundation; either version 3, or (at your option)
9// any later version.
10
11// This library is distributed in the hope that it will be useful,
12// but WITHOUT ANY WARRANTY; without even the implied warranty of
13// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
14// GNU General Public License for more details.
15
16// Under Section 7 of GPL version 3, you are granted additional
17// permissions described in the GCC Runtime Library Exception, version
18// 3.1, as published by the Free Software Foundation.
19
20// You should have received a copy of the GNU General Public License and
21// a copy of the GCC Runtime Library Exception along with this program;
22// see the files COPYING3 and COPYING.RUNTIME respectively. If not, see
23// <http://www.gnu.org/licenses/>.
24
25/** @file experimental/algorithm
26 * This is a TS C++ Library header.
27 */
28
29#ifndef _GLIBCXX_EXPERIMENTAL_ALGORITHM
30#define _GLIBCXX_EXPERIMENTAL_ALGORITHM 1
31
32#pragma GCC system_header
33
34#if __cplusplus <= 201103L
35# include <bits/c++14_warning.h>
36#else
37
38#include <algorithm>
39#include <random>
40#include <experimental/bits/lfts_config.h>
41
42namespace std _GLIBCXX_VISIBILITY(default)
43{
44namespace experimental
45{
46inline namespace fundamentals_v1
47{
48_GLIBCXX_BEGIN_NAMESPACE_VERSION
49
50 template<typename _ForwardIterator, typename _Searcher>
51 inline _ForwardIterator
52 search(_ForwardIterator __first, _ForwardIterator __last,
53 const _Searcher& __searcher)
54 { return __searcher(__first, __last); }
55
56#define __cpp_lib_experimental_sample 201402
57
58 /// Reservoir sampling algorithm.
59 template<typename _InputIterator, typename _RandomAccessIterator,
60 typename _Size, typename _UniformRandomNumberGenerator>
61 _RandomAccessIterator
62 __sample(_InputIterator __first, _InputIterator __last, input_iterator_tag,
63 _RandomAccessIterator __out, random_access_iterator_tag,
64 _Size __n, _UniformRandomNumberGenerator&& __g)
65 {
66 using __distrib_type = std::uniform_int_distribution<_Size>;
67 using __param_type = typename __distrib_type::param_type;
68 __distrib_type __d{};
69 _Size __sample_sz = 0;
70 while (__first != __last && __sample_sz != __n)
71 {
72 __out[__sample_sz++] = *__first;
73 ++__first;
74 }
75 for (auto __pop_sz = __sample_sz; __first != __last;
76 ++__first, (void)++__pop_sz)
77 {
78 const auto __k = __d(__g, __param_type{0, __pop_sz});
79 if (__k < __n)
80 __out[__k] = *__first;
81 }
82 return __out + __sample_sz;
83 }
84
85 /// Selection sampling algorithm.
86 template<typename _ForwardIterator, typename _OutputIterator, typename _Cat,
87 typename _Size, typename _UniformRandomNumberGenerator>
88 _OutputIterator
89 __sample(_ForwardIterator __first, _ForwardIterator __last,
90 forward_iterator_tag,
91 _OutputIterator __out, _Cat,
92 _Size __n, _UniformRandomNumberGenerator&& __g)
93 {
94 using __distrib_type = std::uniform_int_distribution<_Size>;
95 using __param_type = typename __distrib_type::param_type;
96 __distrib_type __d{};
97 _Size __unsampled_sz = std::distance(__first, __last);
98 for (__n = std::min(__n, __unsampled_sz); __n != 0; ++__first)
99 if (__d(__g, __param_type{0, --__unsampled_sz}) < __n)
100 {
101 *__out++ = *__first;
102 --__n;
103 }
104 return __out;
105 }
106
107 /// Take a random sample from a population.
108 template<typename _PopulationIterator, typename _SampleIterator,
109 typename _Distance, typename _UniformRandomNumberGenerator>
110 _SampleIterator
111 sample(_PopulationIterator __first, _PopulationIterator __last,
112 _SampleIterator __out, _Distance __n,
113 _UniformRandomNumberGenerator&& __g)
114 {
115 using __pop_cat = typename
116 std::iterator_traits<_PopulationIterator>::iterator_category;
117 using __samp_cat = typename
118 std::iterator_traits<_SampleIterator>::iterator_category;
119
120 static_assert(
121 __or_<is_convertible<__pop_cat, forward_iterator_tag>,
122 is_convertible<__samp_cat, random_access_iterator_tag>>::value,
123 "output range must use a RandomAccessIterator when input range"
124 " does not meet the ForwardIterator requirements");
125
126 static_assert(is_integral<_Distance>::value,
127 "sample size must be an integer type");
128
129 typename iterator_traits<_PopulationIterator>::difference_type __d = __n;
130 return std::experimental::__sample(
131 __first, __last, __pop_cat{}, __out, __samp_cat{},
132 __d, std::forward<_UniformRandomNumberGenerator>(__g));
133 }
134
135_GLIBCXX_END_NAMESPACE_VERSION
136} // namespace fundamentals_v1
137} // namespace experimental
138} // namespace std
139
140#endif // C++14
141
142#endif // _GLIBCXX_EXPERIMENTAL_ALGORITHM