ShortestPathUtils.java

/*
 * Created on Jul 10, 2005
 *
 * Copyright (c) 2005, the JUNG Project and the Regents of the University 
 * of California
 * All rights reserved.
 *
 * This software is open-source under the BSD license; see either
 * "license.txt" or
 * http://jung.sourceforge.net/license.txt for a description.
 */
package edu.uci.ics.jung.algorithms.shortestpath;

import java.util.LinkedList;
import java.util.List;
import java.util.Map;

import edu.uci.ics.jung.graph.Graph;
import edu.uci.ics.jung.graph.util.Pair;

/**
 * Utilities relating to the shortest paths in a graph.
 */
public class ShortestPathUtils {
	/**
	 * Returns a <code>List</code> of the edges on the shortest path from
	 * <code>source</code> to <code>target</code>, in order of their occurrence
	 * on this path.
	 */
	public static <V, E> List<E> getPath(Graph<V, E> graph,
			ShortestPath<V, E> sp, V source, V target) {
		LinkedList<E> path = new LinkedList<E>();

		Map<V, E> incomingEdges = sp.getIncomingEdgeMap(source);

		if (incomingEdges.isEmpty() || incomingEdges.get(target) == null) {
			return path;
		}
		V current = target;
		while (!current.equals(source)) {
			E incoming = incomingEdges.get(current);
			path.addFirst(incoming);
			Pair<V> endpoints = graph.getEndpoints(incoming);
			if (endpoints.getFirst().equals(current)) {
				current = endpoints.getSecond();
			} else {
				current = endpoints.getFirst();
			}
			// incoming.getOpposite(current);
		}
		return path;
	}
}