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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 Single-Source-Shortest-Path algorithm.
// ==========================================================================
#ifndef INCLUDE_SEQAN_GRAPH_ALGORITHMS_SINGLE_SOURCE_SHORTEST_PATH_H_
#define INCLUDE_SEQAN_GRAPH_ALGORITHMS_SINGLE_SOURCE_SHORTEST_PATH_H_
namespace seqan2 {
// ============================================================================
// Forwards
// ============================================================================
// ============================================================================
// Tags, Classes, Enums
// ============================================================================
// ============================================================================
// Metafunctions
// ============================================================================
// ============================================================================
// Functions
// ============================================================================
// ----------------------------------------------------------------------------
// Function singleSourceShortestPath()
// ----------------------------------------------------------------------------
template <typename TSpec, typename TPredecessorMap, typename TVertexDescriptor, typename TNameMap>
inline void
_printPath(Graph<TSpec> const& g,
TPredecessorMap const& predecessor,
TVertexDescriptor const source,
TVertexDescriptor const v,
TNameMap const& nameMap)
{
if (source == v) {
std::cout << getProperty(nameMap, source);
} else if (getProperty(predecessor, v) == getNil<typename VertexDescriptor<Graph<TSpec> >::Type>()) {
std::cout << "No path from " << getProperty(nameMap, source) << " to " << getProperty(nameMap, v) << " exists.";
} else {
_printPath(g,predecessor, source, getProperty(predecessor, v), nameMap);
std::cout << "," << getProperty(nameMap, v);
}
}
template <typename TSpec, typename TPredecessorMap, typename TVertexDescriptor1, typename TVertexDescriptor2>
inline void
_printPath(Graph<TSpec> const& g,
TPredecessorMap const& predecessor,
TVertexDescriptor1 const source,
TVertexDescriptor2 const v)
{
if (source == v) {
std::cout << source;
} else if (getProperty(predecessor, v) == getNil<typename VertexDescriptor<Graph<TSpec> >::Type>()) {
std::cout << "No path from " << source << " to " << v << " exists.";
} else {
_printPath(g,predecessor, source, getProperty(predecessor, v));
std::cout << "," << v;
}
}
template <typename TSpec, typename TPredecessorMap, typename TVertexDescriptor1, typename TVertexDescriptor2, typename TEdgeSet>
inline bool
_collectEdges(Graph<TSpec> const& g,
TPredecessorMap const& predecessor,
TVertexDescriptor1 const source,
TVertexDescriptor2 const v,
TEdgeSet& edgeSet)
{
if ((TVertexDescriptor1) source == (TVertexDescriptor1) v) {
return true;
} else if (getProperty(predecessor, v) == getNil<typename VertexDescriptor<Graph<TSpec> >::Type>()) {
return false;
} else {
edgeSet.insert(findEdge(g, getProperty(predecessor, v), v));
return _collectEdges(g,predecessor, source, getProperty(predecessor, v), edgeSet);
}
}
//////////////////////////////////////////////////////////////////////////////
template <typename TSpec, typename TPredecessorMap, typename TVertexDescriptor, typename TEdgeSet>
inline bool
_collectEdges(Graph<TSpec> const& g,
TPredecessorMap const& predecessor,
TVertexDescriptor const source,
TEdgeSet& edgeSet)
{
typedef Iterator<Graph<Undirected<> >, VertexIterator>::Type TVertexIterator;
TVertexIterator it(g);
for(;!atEnd(it); goNext(it)) {
if (!_collectEdges(g, predecessor, source, value(it), edgeSet)) {
edgeSet.clear();
return false;
}
}
return true;
}
template <typename TSpec, typename TVertexDescriptor, typename TWeightMap, typename TPredecessorMap, typename TDistanceMap>
inline void
_initializeSingleSource(TPredecessorMap & predecessor,
TDistanceMap & distance,
Graph<TSpec> const & g,
TVertexDescriptor const source,
TWeightMap const & weight)
{
typedef Graph<TSpec> TGraph;
typedef typename Iterator<TGraph, VertexIterator>::Type TVertexIterator;
typedef typename Value<TPredecessorMap>::Type TPredVal;
typedef typename Value<TWeightMap>::Type TDistVal;
TPredVal nilPred = getNil<typename VertexDescriptor<TGraph>::Type>();
TDistVal infDist = _getInfinityDistance(weight);
TVertexIterator it(g);
for(;!atEnd(it);goNext(it)) {
assignProperty(distance, getValue(it), infDist);
assignProperty(predecessor, getValue(it), nilPred);
}
assignProperty(distance, source, 0);
}
template <typename TSpec, typename TWeightMap, typename TPredecessorMap, typename TDistanceMap, typename TVertexDescriptor, typename TEdgeDescriptor>
inline void
_relax(Graph<TSpec> const& g,
TWeightMap const& weight,
TPredecessorMap& predecessor,
TDistanceMap& distance,
TVertexDescriptor const u,
TEdgeDescriptor const e)
{
TVertexDescriptor v = targetVertex(g,e);
if (getProperty(distance, v) > getProperty(distance,u) + getProperty(weight,e)) {
assignProperty(distance, v, getProperty(distance,u) + getProperty(weight,e));
assignProperty(predecessor, v, u);
}
}
// TODO(holtgrew): This looks broken (distance too high below).
/*!
* @fn dagShortestPath
* @headerfile <seqan/graph_algorithms.h>
* @brief Computes shortest paths from a single source in a directed acyclic graph (DAG).
*
* @signature void dagShortestPath(predecessor, distance, g, source, weight);
*
* @param[out] predecessor A property map. A property map that represents predecessor relationships among vertices.
* It determines a shortest-paths tree.
* @param[out] distance A property map. Indicates for each vertex th distance from the source.
* do exist.
* @param[in] g A directed acyclic graph. Types: Directed Graph
* @param[in] source A source vertex. Types: VertexDescriptor
* @param[in] weight A weight map. In a directed acyclic graph edge weights can be negative because no cycles
*
* @section Example
*
* @include demos/dox/graph_algorithms/dag_shortest_path.cpp
*
* @include demos/dox/graph_algorithms/dag_shortest_path.cpp.stdout
*
* @see bellmanFordAlgorithm
* @see dijkstra
*/
template <typename TSpec, typename TVertexDescriptor, typename TWeightMap, typename TPredecessorMap, typename TDistanceMap>
void dagShortestPath(TPredecessorMap & predecessor,
TDistanceMap & distance,
Graph<TSpec> const & g,
TVertexDescriptor const source,
TWeightMap const & weight)
{
typedef typename Iterator<Graph<TSpec>, OutEdgeIterator>::Type TOutEdgeIterator;
typedef typename Iterator<String<TVertexDescriptor>, Rooted>::Type TStringIterator;
// Initialization
resizeVertexMap(predecessor, g);
resizeVertexMap(distance, g);
// Topological sort
String<TVertexDescriptor> order;
topologicalSort(order, g);
_initializeSingleSource(predecessor, distance, g, source, weight);
//DAG Shortest Paths
TStringIterator it = begin(order);
while(!atEnd(it)) {
TOutEdgeIterator itout(g, getValue(it));
for(;!atEnd(itout);++itout) {
_relax(g,weight,predecessor, distance, getValue(it), getValue(itout));
}
goNext(it);
}
}
} // namespace seqan2
#endif // #ifndef INCLUDE_SEQAN_GRAPH_ALGORITHMS_SINGLE_SOURCE_SHORTEST_PATH_H_
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