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/*
Copyright (c) Alexander Zaitsev <zamazan4ik@gmail.com>, 2017
Distributed under the Boost Software License, Version 1.0. (See
accompanying file LICENSE_1_0.txt or copy at
http://www.boost.org/LICENSE_1_0.txt)
See http://www.boost.org/ for latest version.
Based on https://blogs.msdn.microsoft.com/oldnewthing/20170104-00/?p=95115
*/
/// \file apply_permutation.hpp
/// \brief Apply permutation to a sequence.
/// \author Alexander Zaitsev
#ifndef BOOST_ALGORITHM_APPLY_PERMUTATION_HPP
#define BOOST_ALGORITHM_APPLY_PERMUTATION_HPP
#include <algorithm>
#include <type_traits>
#include <boost/config.hpp>
#include <boost/range/begin.hpp>
#include <boost/range/end.hpp>
namespace boost { namespace algorithm
{
/// \fn apply_permutation ( RandomAccessIterator1 item_begin, RandomAccessIterator1 item_end, RandomAccessIterator2 ind_begin )
/// \brief Reorder item sequence with index sequence order
///
/// \param item_begin The start of the item sequence
/// \param item_end One past the end of the item sequence
/// \param ind_begin The start of the index sequence.
///
/// \note Item sequence size should be equal to index size. Otherwise behavior is undefined.
/// Complexity: O(N).
template<typename RandomAccessIterator1, typename RandomAccessIterator2>
void
apply_permutation(RandomAccessIterator1 item_begin, RandomAccessIterator1 item_end,
RandomAccessIterator2 ind_begin, RandomAccessIterator2 ind_end)
{
typedef typename std::iterator_traits<RandomAccessIterator1>::difference_type Diff;
typedef typename std::iterator_traits<RandomAccessIterator2>::difference_type Index;
using std::swap;
Diff size = std::distance(item_begin, item_end);
for (Diff i = 0; i < size; i++)
{
Diff current = i;
while (i != ind_begin[current])
{
Index next = ind_begin[current];
swap(item_begin[current], item_begin[next]);
ind_begin[current] = current;
current = next;
}
ind_begin[current] = current;
}
}
/// \fn apply_reverse_permutation ( RandomAccessIterator1 item_begin, RandomAccessIterator1 item_end, RandomAccessIterator2 ind_begin )
/// \brief Reorder item sequence with index sequence order
///
/// \param item_begin The start of the item sequence
/// \param item_end One past the end of the item sequence
/// \param ind_begin The start of the index sequence.
///
/// \note Item sequence size should be equal to index size. Otherwise behavior is undefined.
/// Complexity: O(N).
template<typename RandomAccessIterator1, typename RandomAccessIterator2>
void
apply_reverse_permutation(
RandomAccessIterator1 item_begin,
RandomAccessIterator1 item_end,
RandomAccessIterator2 ind_begin,
RandomAccessIterator2 ind_end)
{
typedef typename std::iterator_traits<RandomAccessIterator2>::difference_type Diff;
using std::swap;
Diff length = std::distance(item_begin, item_end);
for (Diff i = 0; i < length; i++)
{
while (i != ind_begin[i])
{
Diff next = ind_begin[i];
swap(item_begin[i], item_begin[next]);
swap(ind_begin[i], ind_begin[next]);
}
}
}
/// \fn apply_permutation ( Range1 item_range, Range2 ind_range )
/// \brief Reorder item sequence with index sequence order
///
/// \param item_range The item sequence
/// \param ind_range The index sequence
///
/// \note Item sequence size should be equal to index size. Otherwise behavior is undefined.
/// Complexity: O(N).
template<typename Range1, typename Range2>
void
apply_permutation(Range1& item_range, Range2& ind_range)
{
apply_permutation(boost::begin(item_range), boost::end(item_range),
boost::begin(ind_range), boost::end(ind_range));
}
/// \fn apply_reverse_permutation ( Range1 item_range, Range2 ind_range )
/// \brief Reorder item sequence with index sequence order
///
/// \param item_range The item sequence
/// \param ind_range The index sequence
///
/// \note Item sequence size should be equal to index size. Otherwise behavior is undefined.
/// Complexity: O(N).
template<typename Range1, typename Range2>
void
apply_reverse_permutation(Range1& item_range, Range2& ind_range)
{
apply_reverse_permutation(boost::begin(item_range), boost::end(item_range),
boost::begin(ind_range), boost::end(ind_range));
}
}}
#endif //BOOST_ALGORITHM_APPLY_PERMUTATION_HPP
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