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apply_permutation.hpp
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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