algorithm revision 288943 
1// -*- C++ -*-
2//===-------------------------- algorithm ---------------------------------===//
3//
4//                     The LLVM Compiler Infrastructure
5//
6// This file is dual licensed under the MIT and the University of Illinois Open
7// Source Licenses. See LICENSE.TXT for details.
8//
9//===----------------------------------------------------------------------===//
10
11#ifndef _LIBCPP_EXPERIMENTAL_ALGORITHM
12#define _LIBCPP_EXPERIMENTAL_ALGORITHM
13
14/*
15   experimental/algorithm synopsis
16
17#include <algorithm>
18
19namespace std {
20namespace experimental {
21inline namespace fundamentals_v1 {
22
23template <class ForwardIterator, class Searcher>
24ForwardIterator search(ForwardIterator first, ForwardIterator last,
25                       const Searcher &searcher);
26template <class PopulationIterator, class SampleIterator, class Distance,
27          class UniformRandomNumberGenerator>
28SampleIterator sample(PopulationIterator first, PopulationIterator last,
29                      SampleIterator out, Distance n,
30                      UniformRandomNumberGenerator &&g);
31
32} // namespace fundamentals_v1
33} // namespace experimental
34} // namespace std
35
36*/
37
38#include <experimental/__config>
39#include <algorithm>
40#include <type_traits>
41
42#include <__undef_min_max>
43
44#include <__debug>
45
46#if !defined(_LIBCPP_HAS_NO_PRAGMA_SYSTEM_HEADER)
47#pragma GCC system_header
48#endif
49
50_LIBCPP_BEGIN_NAMESPACE_LFTS
51
52
53template <class _PopulationIterator, class _SampleIterator, class _Distance,
54          class _UniformRandomNumberGenerator>
55_LIBCPP_INLINE_VISIBILITY
56_SampleIterator __sample(_PopulationIterator __first,
57                         _PopulationIterator __last, _SampleIterator __out,
58                         _Distance __n,
59                         _UniformRandomNumberGenerator &&__g,
60                         input_iterator_tag) {
61
62  _Distance __k = 0;
63  for (; __first != __last && __k < __n; ++__first, (void)++__k)
64    __out[__k] = *__first;
65  _Distance __sz = __k;
66  for (; __first != __last; ++__first, (void)++__k) {
67    _Distance __r = _VSTD::uniform_int_distribution<_Distance>(0, __k)(__g);
68    if (__r < __sz)
69      __out[__r] = *__first;
70  }
71  return __out + _VSTD::min(__n, __k);
72}
73
74template <class _PopulationIterator, class _SampleIterator, class _Distance,
75          class _UniformRandomNumberGenerator>
76_LIBCPP_INLINE_VISIBILITY
77_SampleIterator __sample(_PopulationIterator __first,
78                         _PopulationIterator __last, _SampleIterator __out,
79                         _Distance __n,
80                         _UniformRandomNumberGenerator &&__g,
81                         forward_iterator_tag) {
82  _Distance __unsampled_sz = _VSTD::distance(__first, __last);
83  for (__n = _VSTD::min(__n, __unsampled_sz); __n != 0; ++__first) {
84    _Distance __r =
85        _VSTD::uniform_int_distribution<_Distance>(0, --__unsampled_sz)(__g);
86    if (__r < __n) {
87      *__out++ = *__first;
88      --__n;
89    }
90  }
91  return __out;
92}
93
94template <class _PopulationIterator, class _SampleIterator, class _Distance,
95          class _UniformRandomNumberGenerator>
96_LIBCPP_INLINE_VISIBILITY
97_SampleIterator sample(_PopulationIterator __first,
98                         _PopulationIterator __last, _SampleIterator __out,
99                         _Distance __n, _UniformRandomNumberGenerator &&__g) {
100  typedef typename iterator_traits<_PopulationIterator>::iterator_category
101        _PopCategory;
102  typedef typename iterator_traits<_PopulationIterator>::difference_type
103        _Difference;
104  typedef typename common_type<_Distance, _Difference>::type _CommonType;
105  _LIBCPP_ASSERT(__n >= 0, "N must be a positive number.");
106  return _VSTD_LFTS::__sample(
107      __first, __last, __out, _CommonType(__n),
108      _VSTD::forward<_UniformRandomNumberGenerator>(__g),
109      _PopCategory());
110}
111
112_LIBCPP_END_NAMESPACE_LFTS
113
114#endif /* _LIBCPP_EXPERIMENTAL_ALGORITHM */
115