/*
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Copyright (c) Marshall Clow 2008-2012.
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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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Revision history:
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28 Sep 2015 mtc First version
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*/
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/// \file sort_subrange.hpp
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/// \brief Sort a subrange
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/// \author Marshall Clow
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///
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/// Suggested by Sean Parent in his CppCon 2015 keynote
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#ifndef BOOST_ALGORITHM_SORT_SUBRANGE_HPP
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#define BOOST_ALGORITHM_SORT_SUBRANGE_HPP
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#include <functional> // For std::less
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#include <iterator> // For std::iterator_traits
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#include <algorithm> // For nth_element and partial_sort
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#include <boost/config.hpp>
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#include <boost/range/begin.hpp>
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#include <boost/range/end.hpp>
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namespace boost { namespace algorithm {
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/// \fn sort_subrange ( T const& val,
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/// Iterator first, Iterator last,
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/// Iterator sub_first, Iterator sub_last,
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/// Pred p )
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/// \brief Sort the subrange [sub_first, sub_last) that is inside
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/// the range [first, last) as if you had sorted the entire range.
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///
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/// \param first The start of the larger range
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/// \param last The end of the larger range
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/// \param sub_first The start of the sub range
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/// \param sub_last The end of the sub range
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/// \param p A predicate to use to compare the values.
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/// p ( a, b ) returns a boolean.
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///
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template<typename Iterator, typename Pred>
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void sort_subrange (
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Iterator first, Iterator last,
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Iterator sub_first, Iterator sub_last,
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Pred p)
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{
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if (sub_first == sub_last) return; // the empty sub-range is already sorted.
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if (sub_first != first) { // sub-range is at the start, don't need to partition
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(void) std::nth_element(first, sub_first, last, p);
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++sub_first;
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}
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std::partial_sort(sub_first, sub_last, last, p);
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}
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template<typename Iterator>
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void sort_subrange (Iterator first, Iterator last, Iterator sub_first, Iterator sub_last)
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{
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typedef typename std::iterator_traits<Iterator>::value_type value_type;
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return sort_subrange(first, last, sub_first, sub_last, std::less<value_type>());
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}
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/// range versions?
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/// \fn partition_subrange ( T const& val,
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/// Iterator first, Iterator last,
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/// Iterator sub_first, Iterator sub_last,
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/// Pred p )
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/// \brief Gather the elements of the subrange [sub_first, sub_last) that is
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/// inside the range [first, last) as if you had sorted the entire range.
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///
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/// \param first The start of the larger range
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/// \param last The end of the larger range
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/// \param sub_first The start of the sub range
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/// \param sub_last The end of the sub range
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/// \param p A predicate to use to compare the values.
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/// p ( a, b ) returns a boolean.
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///
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template<typename Iterator, typename Pred>
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void partition_subrange (
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Iterator first, Iterator last,
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Iterator sub_first, Iterator sub_last,
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Pred p)
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{
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if (sub_first != first) {
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(void) std::nth_element(first, sub_first, last, p);
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++sub_first;
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}
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if (sub_last != last)
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(void) std::nth_element(sub_first, sub_last, last, p);
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}
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template<typename Iterator>
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void partition_subrange (Iterator first, Iterator last, Iterator sub_first, Iterator sub_last)
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{
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typedef typename std::iterator_traits<Iterator>::value_type value_type;
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return partition_subrange(first, last, sub_first, sub_last, std::less<value_type>());
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}
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}}
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#endif // BOOST_ALGORITHM_SORT_SUBRANGE_HPP
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