//----------------------------------------------------------------------------
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/// @file pivot.hpp
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/// @brief This file contains the description of several low level algorithms
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///
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/// @author Copyright (c) 2010 2015 Francisco José Tapia (fjtapia@gmail.com )\n
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/// Distributed under the Boost Software License, Version 1.0.\n
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/// ( See accompanying file LICENSE_1_0.txt or copy at
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/// http://www.boost.org/LICENSE_1_0.txt )
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/// @version 0.1
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///
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/// @remarks
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//-----------------------------------------------------------------------------
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#ifndef __BOOST_SORT_COMMON_PIVOT_HPP
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#define __BOOST_SORT_COMMON_PIVOT_HPP
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#include <cstdint>
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namespace boost
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{
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namespace sort
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{
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namespace common
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{
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//
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//##########################################################################
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// ##
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// G L O B A L V A R I B L E S ##
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// ##
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//##########################################################################
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//
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//-----------------------------------------------------------------------------
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// function : mid3
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/// @brief : return the iterator to the mid value of the three values passsed
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/// as parameters
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//
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/// @param iter_1 : iterator to the first value
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/// @param iter_2 : iterator to the second value
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/// @param iter_3 : iterator to the third value
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/// @param comp : object for to compare two values
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/// @return iterator to mid value
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//-----------------------------------------------------------------------------
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template < typename Iter_t, typename Compare >
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inline Iter_t mid3 (Iter_t iter_1, Iter_t iter_2, Iter_t iter_3, Compare comp)
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{
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if (comp (*iter_2, *iter_1)) std::swap ( *iter_2, *iter_1);
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if (comp (*iter_3, *iter_2))
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{ std::swap ( *iter_3, *iter_2);
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if (comp (*iter_2, *iter_1)) std::swap ( *iter_2, *iter_1);
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};
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return iter_2;
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};
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//
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//-----------------------------------------------------------------------------
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// function : pivot3
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/// @brief : receive a range between first and last, calcule the mid iterator
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/// with the first, the previous to the last, and the central
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/// position. With this mid iterator swap with the first position
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//
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/// @param first : iterator to the first element
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/// @param last : iterator to the last element
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/// @param comp : object for to compare two elements
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//-----------------------------------------------------------------------------
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template < class Iter_t, class Compare >
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inline void pivot3 (Iter_t first, Iter_t last, Compare comp)
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{
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auto N2 = (last - first) >> 1;
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Iter_t it_val = mid3 (first + 1, first + N2, last - 1, comp);
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std::swap (*first, *it_val);
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};
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//
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//-----------------------------------------------------------------------------
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// function : mid9
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/// @brief : return the iterator to the mid value of the nine values passsed
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/// as parameters
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//
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/// @param iter_1 : iterator to the first value
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/// @param iter_2 : iterator to the second value
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/// @param iter_3 : iterator to the third value
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/// @param iter_4 : iterator to the fourth value
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/// @param iter_5 : iterator to the fifth value
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/// @param iter_6 : iterator to the sixth value
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/// @param iter_7 : iterator to the seventh value
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/// @param iter_8 : iterator to the eighth value
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/// @param iter_9 : iterator to the ninth value
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/// @return iterator to the mid value
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//-----------------------------------------------------------------------------
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template < class Iter_t, class Compare >
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inline Iter_t mid9 (Iter_t iter_1, Iter_t iter_2, Iter_t iter_3, Iter_t iter_4,
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Iter_t iter_5, Iter_t iter_6, Iter_t iter_7, Iter_t iter_8,
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Iter_t iter_9, Compare comp)
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{
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return mid3 (mid3 (iter_1, iter_2, iter_3, comp),
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mid3 (iter_4, iter_5, iter_6, comp),
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mid3 (iter_7, iter_8, iter_9, comp), comp);
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};
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//
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//-----------------------------------------------------------------------------
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// function : pivot9
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/// @brief : receive a range between first and last, obtain 9 values between
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/// the elements including the first and the previous to the last.
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/// Obtain the iterator to the mid value and swap with the first
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/// position
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//
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/// @param first : iterator to the first element
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/// @param last : iterator to the last element
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/// @param comp : object for to compare two elements
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//-----------------------------------------------------------------------------
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template < class Iter_t, class Compare >
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inline void pivot9 (Iter_t first, Iter_t last, Compare comp)
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{
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size_t cupo = (last - first) >> 3;
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Iter_t itaux = mid9 (first + 1, first + cupo, first + 2 * cupo,
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first + 3 * cupo, first + 4 * cupo, first + 5 * cupo,
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first + 6 * cupo, first + 7 * cupo, last - 1, comp);
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std::swap (*first, *itaux);
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};
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//****************************************************************************
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};// End namespace common
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};// End namespace sort
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};// End namespace boost
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//****************************************************************************
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#endif
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