org.jgrapht.alg.shortestpath.BaseMultiObjectiveShortestPathAlgorithm Maven / Gradle / Ivy
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/*
* (C) Copyright 2017-2023, by Dimitrios Michail and Contributors.
*
* JGraphT : a free Java graph-theory library
*
* See the CONTRIBUTORS.md file distributed with this work for additional
* information regarding copyright ownership.
*
* This program and the accompanying materials are made available under the
* terms of the Eclipse Public License 2.0 which is available at
* http://www.eclipse.org/legal/epl-2.0, or the
* GNU Lesser General Public License v2.1 or later
* which is available at
* http://www.gnu.org/licenses/old-licenses/lgpl-2.1-standalone.html.
*
* SPDX-License-Identifier: EPL-2.0 OR LGPL-2.1-or-later
*/
package org.jgrapht.alg.shortestpath;
import org.jgrapht.*;
import org.jgrapht.alg.interfaces.*;
import org.jgrapht.graph.*;
import java.util.*;
/**
* A base implementation of the multi-objective shortest path interface.
*
* @param the graph vertex type
* @param the graph edge type
*
* @author Dimitrios Michail
*/
abstract class BaseMultiObjectiveShortestPathAlgorithm
implements MultiObjectiveShortestPathAlgorithm
{
/**
* Error message for reporting that a source vertex is missing.
*/
static final String GRAPH_MUST_CONTAIN_THE_SOURCE_VERTEX =
"Graph must contain the source vertex!";
/**
* Error message for reporting that a sink vertex is missing.
*/
static final String GRAPH_MUST_CONTAIN_THE_SINK_VERTEX = "Graph must contain the sink vertex!";
/**
* The underlying graph.
*/
protected final Graph graph;
/**
* Constructs a new instance of the algorithm for a given graph
*
* @param graph the graph
*/
public BaseMultiObjectiveShortestPathAlgorithm(Graph graph)
{
this.graph = Objects.requireNonNull(graph, "Graph is null");
}
@Override
public MultiObjectiveSingleSourcePaths getPaths(V source)
{
if (!graph.containsVertex(source)) {
throw new IllegalArgumentException(GRAPH_MUST_CONTAIN_THE_SOURCE_VERTEX);
}
Map>> paths = new HashMap<>();
for (V v : graph.vertexSet()) {
paths.put(v, getPaths(source, v));
}
return new ListMultiObjectiveSingleSourcePathsImpl<>(graph, source, paths);
}
/**
* Create an empty path. Returns null if the source vertex is different than the target vertex.
*
* @param source the source vertex
* @param sink the sink vertex
* @return an empty path or null null if the source vertex is different than the target vertex
*/
protected final GraphPath createEmptyPath(V source, V sink)
{
if (source.equals(sink)) {
return GraphWalk.singletonWalk(graph, source, 0d);
} else {
return null;
}
}
}