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1 | // <experimental/algorithm> -*- C++ -*- |
2 | ||
3 | // Copyright (C) 2014 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 | ||
41 | namespace std _GLIBCXX_VISIBILITY(default) | |
42 | { | |
43 | namespace experimental | |
44 | { | |
45 | inline namespace fundamentals_v1 | |
46 | { | |
47 | _GLIBCXX_BEGIN_NAMESPACE_VERSION | |
48 | ||
49 | template<typename _ForwardIterator, typename _Searcher> | |
50 | inline _ForwardIterator | |
51 | search(_ForwardIterator __first, _ForwardIterator __last, | |
52 | const _Searcher& __searcher) | |
53 | { return __searcher(__first, __last); } | |
54 | ||
55 | #define __cpp_lib_experimental_sample 201402 | |
56 | ||
57 | /// Reservoir sampling algorithm. | |
58 | template<typename _InputIterator, typename _RandomAccessIterator, | |
59 | typename _Size, typename _UniformRandomNumberGenerator> | |
60 | _RandomAccessIterator | |
61 | __sample(_InputIterator __first, _InputIterator __last, input_iterator_tag, | |
62 | _RandomAccessIterator __out, random_access_iterator_tag, | |
63 | _Size __n, _UniformRandomNumberGenerator&& __g) | |
64 | { | |
65 | using __distrib_type = std::uniform_int_distribution<_Size>; | |
66 | using __param_type = typename __distrib_type::param_type; | |
67 | __distrib_type __d{}; | |
68 | _Size __sample_sz = 0; | |
69 | while (__first != __last && __sample_sz != __n) | |
70 | __out[__sample_sz++] = *__first++; | |
71 | for (auto __pop_sz = __sample_sz; __first != __last; | |
72 | ++__first, ++__pop_sz) | |
73 | { | |
74 | const auto __k = __d(__g, __param_type{0, __pop_sz}); | |
75 | if (__k < __n) | |
76 | __out[__k] = *__first; | |
77 | } | |
78 | return __out + __sample_sz; | |
79 | } | |
80 | ||
81 | /// Selection sampling algorithm. | |
82 | template<typename _ForwardIterator, typename _OutputIterator, typename _Cat, | |
83 | typename _Size, typename _UniformRandomNumberGenerator> | |
84 | _OutputIterator | |
85 | __sample(_ForwardIterator __first, _ForwardIterator __last, | |
86 | forward_iterator_tag, | |
87 | _OutputIterator __out, _Cat, | |
88 | _Size __n, _UniformRandomNumberGenerator&& __g) | |
89 | { | |
90 | using __distrib_type = std::uniform_int_distribution<_Size>; | |
91 | using __param_type = typename __distrib_type::param_type; | |
92 | __distrib_type __d{}; | |
93 | _Size __unsampled_sz = std::distance(__first, __last); | |
94 | for (__n = std::min(__n, __unsampled_sz); __n != 0; ++__first) | |
95 | if (__d(__g, __param_type{0, --__unsampled_sz}) < __n) | |
96 | { | |
97 | *__out++ = *__first; | |
98 | --__n; | |
99 | } | |
100 | return __out; | |
101 | } | |
102 | ||
103 | /// Take a random sample from a population. | |
104 | template<typename _PopulationIterator, typename _SampleIterator, | |
105 | typename _Distance, typename _UniformRandomNumberGenerator> | |
106 | _SampleIterator | |
107 | sample(_PopulationIterator __first, _PopulationIterator __last, | |
108 | _SampleIterator __out, _Distance __n, | |
109 | _UniformRandomNumberGenerator&& __g) | |
110 | { | |
111 | using __pop_cat = typename | |
112 | std::iterator_traits<_PopulationIterator>::iterator_category; | |
113 | using __samp_cat = typename | |
114 | std::iterator_traits<_SampleIterator>::iterator_category; | |
115 | ||
116 | static_assert( | |
117 | __or_<is_convertible<__pop_cat, forward_iterator_tag>, | |
118 | is_convertible<__samp_cat, random_access_iterator_tag>>::value, | |
119 | "output range must use a RandomAccessIterator when input range" | |
120 | " does not meet the ForwardIterator requirements"); | |
121 | ||
122 | static_assert(is_integral<_Distance>::value, | |
123 | "sample size must be an integer type"); | |
124 | ||
125 | return std::experimental::__sample( | |
126 | __first, __last, __pop_cat{}, __out, __samp_cat{}, | |
127 | __n, std::forward<_UniformRandomNumberGenerator>(__g)); | |
128 | } | |
129 | ||
130 | _GLIBCXX_END_NAMESPACE_VERSION | |
131 | } // namespace fundamentals_v1 | |
132 | } // namespace experimental | |
133 | } // namespace std | |
134 | ||
135 | #endif // C++14 | |
136 | ||
137 | #endif // _GLIBCXX_EXPERIMENTAL_ALGORITHM |