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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 Kruskal's algorithm.
// ==========================================================================
#ifndef INCLUDE_SEQAN_GRAPH_ALGORITHMS_KRUSKAL_H_
#define INCLUDE_SEQAN_GRAPH_ALGORITHMS_KRUSKAL_H_
namespace seqan2 {
// ============================================================================
// Forwards
// ============================================================================
// ============================================================================
// Tags, Classes, Enums
// ============================================================================
// ============================================================================
// Metafunctions
// ============================================================================
// ============================================================================
// Functions
// ============================================================================
// ----------------------------------------------------------------------------
// Function kruskalsAlgorithm()
// ----------------------------------------------------------------------------
template <typename TWeight, typename TPair>
struct LessPairI1_ : public std::function<bool(Pair<TWeight, TPair>)>
{
bool operator() (Pair<TWeight, TPair> const & a1,
Pair<TWeight, TPair> const & a2) const
{
return (a1.i1 < a2.i1);
}
};
/*!
* @fn kruskalsAlgorithm
* @headerfile <seqan/graph_algorithms.h>
* @brief Computes a minimum spanning tree on a graph.
*
* @signature void kruskalsAlgorithm(edges, g, source, weight);
*
* @param[out] edges A String of vertex descriptors that represent edges. Each consecutive pair is an edge with the
* two end points.
* @param[in] g An undirected graph. Types: Undirected Graph
* @param[in] source A source vertex. Types: VertexDescriptor
* @param[in] weight Edge weights.
*
* @section Example
*
* @include demos/dox/graph_algorithms/kruskals_algorithm.cpp
*
* @include demos/dox/graph_algorithms/kruskals_algorithm.cpp.stdout
*
* @see primsAlgorithm
*/
template <typename TSpec, typename TVertexDescriptor, typename TWeightMap, typename TEdges>
void kruskalsAlgorithm(TEdges & edges,
Graph<TSpec> const & g,
TVertexDescriptor const,
TWeightMap const & weight)
{
typedef Graph<TSpec> TGraph;
typedef typename Iterator<TGraph, EdgeIterator>::Type TEdgeIterator;
typedef typename Value<TWeightMap>::Type TWeight;
typedef Pair<TVertexDescriptor, TVertexDescriptor> TVertexPair;
typedef Pair<TWeight, TVertexPair> TWeightEdgePair;
typedef String<TWeightEdgePair> TEdgeList;
typedef typename Iterator<TEdgeList>::Type TEdgeListIter;
TEdgeList edgeList;
// Initialization
reserve(edges, 2 * (numVertices(g) - 1));
UnionFind<TVertexDescriptor> unionFind;
resizeVertexMap(unionFind, g);
// Sort the edges
TEdgeIterator itE(g);
for(;!atEnd(itE);goNext(itE)) appendValue(edgeList, TWeightEdgePair(getProperty(weight, getValue(itE)), TVertexPair(sourceVertex(itE),targetVertex(itE))));
std::sort(begin(edgeList, Standard() ), end(edgeList, Standard() ), LessPairI1_<TWeight, TVertexPair>() );
// Process each edge
TEdgeListIter itEdgeList = begin(edgeList, Standard());
TEdgeListIter itEdgeListEnd = end(edgeList, Standard());
for (; itEdgeList != itEdgeListEnd; goNext(itEdgeList)) {
TVertexDescriptor x = value(itEdgeList).i2.i1;
TVertexDescriptor y = value(itEdgeList).i2.i2;
if (findSet(unionFind, x) == findSet(unionFind, y))
continue;
appendValue(edges, x);
appendValue(edges, y);
joinSets(unionFind, findSet(unionFind, x), findSet(unionFind, y));
}
}
} // namespace seqan2
#endif // #ifndef INCLUDE_SEQAN_GRAPH_ALGORITHMS_KRUSKAL_H_
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