/*
* GeoTools - The Open Source Java GIS Toolkit
* http://geotools.org
*
* (C) 2002-2008, Open Source Geospatial Foundation (OSGeo)
*
* This library is free software; you can redistribute it and/or
* modify it under the terms of the GNU Lesser General Public
* License as published by the Free Software Foundation;
* version 2.1 of the License.
*
* This library is distributed in the hope that it will be useful,
* but WITHOUT ANY WARRANTY; without even the implied warranty of
* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
* Lesser General Public License for more details.
*/
package org.geotools.graph.traverse.standard;
import org.geotools.graph.structure.Graph;
import org.geotools.graph.util.Queue;
import org.geotools.graph.util.Stack;
/**
* Iterates over the nodes of a graph in <B>Depth First Topological Sort</B>
* pattern. The following is an illustration of the iteration.<BR>
* <IMG src="doc-files/depth_topo.gif"><BR>
* <BR>
* Initially all nodes of degree less than two are <B>active</B>
* (ready to be visited). As nodes are visited, a node can become active
* when all but one of its related nodes have been visited (
* degree = counter + 1). When a node becomes active it is placed into the
* <B>active node queue</B> (queue of nodes to be visited).
* The Depth First Topological iterator places
* nodes into the queue in <B>Last In First Out</B> order (a Stack).<BR>
* <BR>
* To determine when a node is to become active the iterator uses the counter
* associated with each node. If these counters are modified by an entity
* other then the iterator, the iteration may be affected in undefined ways.
*
* @author Justin Deoliveira, Refractions Research Inc, jdeolive@refractions.net
*
*
*
* @source $URL$
*/
public class DepthFirstTopologicalIterator
extends BreadthFirstTopologicalIterator {
/**
* Builds the active node queue.
*
* @param graph The Graph whose components are being iterated over.
*
* @return A last in first out queue (a stack)
*/
protected Queue buildQueue(Graph graph) {
return(new Stack(graph.getNodes().size()));
}
}