Merge pull request #39 from ZaMaZaN4iK/feature_branch/apply_permutation

Apply_permutation

include/boost/algorithm/apply_permutation.hpp

@@ -0,0 +1,125 @@
+/*
+  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, RandomAccessIterator2 ind_end)
+{
+    using Diff = typename std::iterator_traits<RandomAccessIterator1>::difference_type;
+    using std::swap;
+    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];
+            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)
+{
+    using Diff = typename std::iterator_traits<RandomAccessIterator2>::difference_type;
+    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