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// ==========================================================================
// SeqAn - The Library for Sequence Analysis
// ==========================================================================
// Copyright (c) 2006-2026, Knut Reinert, FU Berlin
// All rights reserved.
//
// Redistribution and use in source and binary forms, with or without
// modification, are permitted provided that the following conditions are met:
//
// * Redistributions of source code must retain the above copyright
// notice, this list of conditions and the following disclaimer.
// * Redistributions in binary form must reproduce the above copyright
// notice, this list of conditions and the following disclaimer in the
// documentation and/or other materials provided with the distribution.
// * Neither the name of Knut Reinert or the FU Berlin nor the names of
// its contributors may be used to endorse or promote products derived
// from this software without specific prior written permission.
//
// THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS"
// AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
// IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
// ARE DISCLAIMED. IN NO EVENT SHALL KNUT REINERT OR THE FU BERLIN BE LIABLE
// FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
// DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR
// SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER
// CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
// LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
// OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH
// DAMAGE.
//
// ==========================================================================
// Author: Tobias Raussch <rausch@embl.de>
// ==========================================================================
// Implementation of the Floyd-Warshall algorithm.
// ==========================================================================
#ifndef INCLUDE_SEQAN_GRAPH_ALGORITHMS_FLOYD_WARSHALL_H_
#define INCLUDE_SEQAN_GRAPH_ALGORITHMS_FLOYD_WARSHALL_H_
namespace seqan2 {
// ============================================================================
// Forwards
// ============================================================================
// ============================================================================
// Tags, Classes, Enums
// ============================================================================
// ============================================================================
// Metafunctions
// ============================================================================
// ============================================================================
// Functions
// ============================================================================
// ----------------------------------------------------------------------------
// Function floydWarshallAlgorithm()
// ----------------------------------------------------------------------------
/*!
* @fn floydWarshallAlgorithm
* @headerfile <seqan/graph_algorithms.h>
* @brief Finds shortest paths between all pairs of vertices in a graph.
*
* @signature void floydWarshallAlgorithm(g, weight, distance, predecessor);
*
* @param[out] predecessor A matrix with predecessors. Entry (i,j) in this matrix indicates the predecessor of j on
* a shortest path from vertex i to vertex j. You can use <tt>_printAllPairsShortestPath(g,
* predecessor, i, j)</tt> to print the shortest path from i to j. Types: Matrix
* @param[out] distance A matrix with distances.Entry (i,j) in this matrix indicates the distance from vertex i
* to vertex j. Types: Matrix
* @param[in] weight A weight map. A property map with edge weights. Edge weights may be negative.
* @param[in] g A directed graph. Types: Directed Graph
*
* The graph must be free of negative-weight cycles.
*
* @section Example
*
* @include demos/dox/graph_algorithms/floyd_warshall_algorithm.cpp
*
* @include demos/dox/graph_algorithms/floyd_warshall_algorithm.cpp.stdout
*
* @see allPairsShortestPath
*/
template <typename TSpec, typename TWeightMap, typename TMatrix, typename TPredecessor>
void floydWarshallAlgorithm(TMatrix & distMatrix,
TPredecessor & predecessor,
Graph<TSpec> const & g,
TWeightMap const & weight)
{
typedef typename Size<TMatrix>::Type TSize;
typedef typename Value<TMatrix>::Type TMatrixVal;
// Initialize first distance matrix
_initializeAllPairs(g,weight,distMatrix,predecessor);
// Floyd-Warshall
TSize len = (TSize) std::sqrt((double) length(distMatrix));
TMatrix local = distMatrix;
for(TSize k=0;k<len;++k) {
for(TSize i=0;i<len;++i) {
for(TSize j=0;j<len;++j) {
TMatrixVal min1 = getValue(distMatrix, i*len+j);
TMatrixVal min2 = getValue(distMatrix, i*len+k) + getValue(distMatrix, k*len + j);
if (min2 < min1) {
assignValue(local, i*len+j,min2);
assignValue(predecessor, i*len+j,getValue(predecessor, k*len+j));
} else {
assignValue(local, i*len+j,min1);
assignValue(predecessor, i*len+j, getValue(predecessor, i*len+j));
}
}
}
distMatrix=local;
}
}
} // namespace seqan2
#endif // #ifndef INCLUDE_SEQAN_GRAPH_ALGORITHMS_FLOYD_WARSHALL_H_
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