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Added initial for apply_permutation

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This commit is contained in:
Alexander Zaitsev
2017-05-18 20:38:07 -06:00
parent 5d76dab9b8
commit 1ed284d696
2 changed files with 190 additions and 0 deletions
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68
example/apply_permutation_example.cpp Normal file
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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.
*/
#include <vector>
#include <iostream>
#include <boost/algorithm/apply_permutation.hpp>
namespace ba = boost::algorithm;
int main ( int /*argc*/, char * /*argv*/ [] )
{
{
std::cout << "apply_permutation with iterators:\n";
std::vector<int> vec{1, 2, 3, 4, 5}, order{4, 2, 3, 1, 0};
ba::apply_permutation(vec.begin(), vec.end(), order.begin());
for (const auto& x : vec)
{
std::cout << x << ", ";
}
std::cout << std::endl;
}
{
std::cout << "apply_reverse_permutation with iterators:\n";
std::vector<int> vec{1, 2, 3, 4, 5}, order{4, 2, 3, 1, 0};
ba::apply_reverse_permutation(vec.begin(), vec.end(), order.begin());
for (const auto& x : vec)
{
std::cout << x << ", ";
}
std::cout << std::endl;
}
{
std::cout << "apply_reverse_permutation with ranges:\n";
std::vector<int> vec{1, 2, 3, 4, 5}, order{4, 2, 3, 1, 0};
ba::apply_reverse_permutation(vec, order);
for (const auto& x : vec)
{
std::cout << x << ", ";
}
std::cout << std::endl;
}
{
std::cout << "apply_permutation with ranges:\n";
std::vector<int> vec{1, 2, 3, 4, 5}, order{4, 2, 3, 1, 0};
ba::apply_permutation(vec, order);
for (const auto& x : vec)
{
std::cout << x << ", ";
}
std::cout << std::endl;
}
return 0;
}

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include/boost/algorithm/apply_permutation.hpp Normal file
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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/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)
{
using Diff = typename std::iterator_traits<RandomAccessIterator1>::difference_type;
Diff size = std::distance(item_begin, item_end);
for (Diff i = 0; i < size; i++)
{
auto current = i;
while (i != ind_begin[current])
{
auto next = ind_begin[current];
std::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)
{
using Diff = typename std::iterator_traits<RandomAccessIterator2>::difference_type;
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];
std::swap(item_begin[i], item_begin[next]);
std::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));
}
/// \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));
}
}}
#endif //BOOST_ALGORITHM_APPLY_PERMUTATION_HPP