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JGraphT is a free Java graph library
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/* ==========================================
* JGraphT : a free Java graph-theory library
* ==========================================
*
* Project Info: http://jgrapht.sourceforge.net/
* Project Creator: Barak Naveh (http://sourceforge.net/users/barak_naveh)
*
* (C) Copyright 2003-2007, by Barak Naveh and Contributors.
*
* 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; either version 2.1 of the License, or
* (at your option) any later version.
*
* 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.
*
* You should have received a copy of the GNU Lesser General Public License
* along with this library; if not, write to the Free Software Foundation,
* Inc.,
* 59 Temple Place, Suite 330, Boston, MA 02111-1307, USA.
*/
/* -------------------------
* BreadthFirstIterator.java
* -------------------------
* (C) Copyright 2003-2007, by Barak Naveh and Contributors.
*
* Original Author: Barak Naveh
* Contributor(s): Liviu Rau
* Christian Hammer
*
* $Id: BreadthFirstIterator.java 568 2007-09-30 00:12:18Z perfecthash $
*
* Changes
* -------
* 24-Jul-2003 : Initial revision (BN);
* 06-Aug-2003 : Extracted common logic to TraverseUtils.XXFirstIterator (BN);
* 31-Jan-2004 : Reparented and changed interface to parent class (BN);
*
*/
package org.jgrapht.traverse;
import java.util.*;
import org.jgrapht.*;
/**
* A breadth-first iterator for a directed and an undirected graph. For this
* iterator to work correctly the graph must not be modified during iteration.
* Currently there are no means to ensure that, nor to fail-fast. The results of
* such modifications are undefined.
*
* @author Barak Naveh
* @since Jul 19, 2003
*/
public class BreadthFirstIterator
extends CrossComponentIterator
{
//~ Instance fields --------------------------------------------------------
/**
* Note to users: this queue implementation is a bit lame in terms of
* GC efficiency. If you need it to be improved either let us know or use
* the source...
*/
private LinkedList queue = new LinkedList();
//~ Constructors -----------------------------------------------------------
/**
* Creates a new breadth-first iterator for the specified graph.
*
* @param g the graph to be iterated.
*/
public BreadthFirstIterator(Graph g)
{
this(g, null);
}
/**
* Creates a new breadth-first iterator for the specified graph. Iteration
* will start at the specified start vertex and will be limited to the
* connected component that includes that vertex. If the specified start
* vertex is null, iteration will start at an arbitrary vertex
* and will not be limited, that is, will be able to traverse all the graph.
*
* @param g the graph to be iterated.
* @param startVertex the vertex iteration to be started.
*/
public BreadthFirstIterator(Graph g, V startVertex)
{
super(g, startVertex);
}
//~ Methods ----------------------------------------------------------------
/**
* @see CrossComponentIterator#isConnectedComponentExhausted()
*/
protected boolean isConnectedComponentExhausted()
{
return queue.isEmpty();
}
/**
* @see CrossComponentIterator#encounterVertex(Object, Object)
*/
protected void encounterVertex(V vertex, E edge)
{
putSeenData(vertex, null);
queue.add(vertex);
}
/**
* @see CrossComponentIterator#encounterVertexAgain(Object, Object)
*/
protected void encounterVertexAgain(V vertex, E edge)
{
}
/**
* @see CrossComponentIterator#provideNextVertex()
*/
protected V provideNextVertex()
{
return queue.removeFirst();
}
}
// End BreadthFirstIterator.java