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https://github.com/bolero-MURAKAMI/Sprout.git
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83 lines
3 KiB
C++
83 lines
3 KiB
C++
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/*=============================================================================
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Copyright (c) 2011-2014 Bolero MURAKAMI
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https://github.com/bolero-MURAKAMI/Sprout
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Distributed under the Boost Software License, Version 1.0. (See accompanying
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file LICENSE_1_0.txt or copy at http://www.boost.org/LICENSE_1_0.txt)
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=============================================================================*/
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#ifndef SPROUT_ALGORITHM_CXX14_SAMPLE_HPP
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#define SPROUT_ALGORITHM_CXX14_SAMPLE_HPP
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#include <iterator>
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#include <sprout/config.hpp>
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#include <sprout/utility/forward.hpp>
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#include <sprout/iterator/distance.hpp>
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#include <sprout/workaround/detail/uniform_int_distribution.hpp>
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#include HDR_ALGORITHM_MIN_MAX_SSCRISK_CEL_OR_SPROUT
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namespace sprout {
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namespace detail {
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template<typename PopIterator, typename SampleIterator, typename Size, typename URNG>
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inline SPROUT_CXX14_CONSTEXPR SampleIterator
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sample_impl(
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PopIterator first, PopIterator last, std::input_iterator_tag*,
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SampleIterator out, std::random_access_iterator_tag*,
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Size n, URNG&& g
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)
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{
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typedef SPROUT_WORKAROUND_DETAIL_UNIFORM_INT_DISTRIBUTION<Size> distribution_type;
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typedef typename distribution_type::param_type param_type;
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distribution_type dist = {};
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Size sample_size = 0;
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while (first != last && sample_size != n) {
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out[sample_size++] = *first++;
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}
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for (Size pop_size = sample_size; first != last; ++first, ++pop_size) {
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param_type const p(0, pop_size);
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Size const k = dist(g, p);
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if (k < n) {
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out[k] = *first;
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}
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}
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return out + sample_size;
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}
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template<typename PopIterator, typename SampleIterator, typename Size, typename URNG>
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inline SPROUT_CXX14_CONSTEXPR SampleIterator
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sample_impl(
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PopIterator first, PopIterator last, std::forward_iterator_tag*,
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SampleIterator out, std::output_iterator_tag*,
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Size n, URNG&& g
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)
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{
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typedef SPROUT_WORKAROUND_DETAIL_UNIFORM_INT_DISTRIBUTION<Size> distribution_type;
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typedef typename distribution_type::param_type param_type;
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distribution_type dist = {};
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Size unsampled_size = sprout::distance(first, last);
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for (n = NS_SSCRISK_CEL_OR_SPROUT::min(n, unsampled_size); n != 0; ++first ) {
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param_type const p(0, --unsampled_size);
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if (dist(g, p) < n) {
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*out++ = *first;
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--n;
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}
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}
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return out;
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}
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} // namespace detail
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//
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// sample
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//
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template<typename PopIterator, typename SampleIterator, typename Size, typename URNG>
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inline SPROUT_CXX14_CONSTEXPR SampleIterator
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sample(PopIterator first, PopIterator last, SampleIterator out, Size n, URNG&& g) {
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typedef typename std::iterator_traits<PopIterator>::iterator_category* pop_category;
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typedef typename std::iterator_traits<SampleIterator>::iterator_category* sample_category;
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return sprout::detail::sample_impl(
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first, last, pop_category(),
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out, sample_category(),
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n, SPROUT_FORWARD(URNG, g)
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);
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}
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} // namespace sprout
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#endif // #ifndef SPROUT_ALGORITHM_CXX14_SAMPLE_HPP
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