org.jgrapht.experimental.isomorphism.VertexDegreeEquivalenceComparator Maven / Gradle / Ivy
/* ==========================================
* 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 2003-2008, by Barak Naveh and Contributors.
*
* This program and the accompanying materials are dual-licensed under
* either
*
* (a) the terms of the GNU Lesser General Public License version 2.1
* as published by the Free Software Foundation, or (at your option) any
* later version.
*
* or (per the licensee's choosing)
*
* (b) the terms of the Eclipse Public License v1.0 as published by
* the Eclipse Foundation.
*/
/* -----------------
* VertexDegreeEquivalenceComparator.java
* -----------------
* (C) Copyright 2005-2008, by Assaf Lehr and Contributors.
*
* Original Author: Assaf Lehr
* Contributor(s): -
*
* $Id: VertexDegreeEquivalenceComparator.java 485 2006-06-26 09:12:14Z
* perfecthash $
*
* Changes
* -------
*/
package org.jgrapht.experimental.isomorphism;
import org.jgrapht.*;
import org.jgrapht.experimental.equivalence.*;
/**
* Two vertexes are equivalent under this comparator if and only if:
*
*
* - they have the same IN degree
*
*
AND
*
- they have the same OUT degree
*
*
* @author Assaf
* @since Jul 21, 2005
*/
public class VertexDegreeEquivalenceComparator
implements EquivalenceComparator>
{
/**
*/
public VertexDegreeEquivalenceComparator()
{
}
/**
* Compares the in degrees and the out degrees of the two vertexes.
*
* One may reside in an Undirected Graph and the other in a Directed
* graph, or both on the same graph type.
*
* @see EquivalenceComparator#equivalenceCompare(Object, Object, Object,
* Object)
*/
@Override public boolean equivalenceCompare(
V vertex1,
V vertex2,
Graph context1,
Graph context2)
{
// note that VertexDegreeComparator cannot be used. It supports only
// directed graphs.
InOutDegrees inOut1 = getInOutDegrees(context1, vertex1);
InOutDegrees inOut2 = getInOutDegrees(context2, vertex2);
boolean result = inOut1.equals(inOut2);
return result;
}
/**
* Hashes using the in and out degree of a vertex
*
* @see EquivalenceComparator#equivalenceHashcode(Object, Object)
*/
@Override public int equivalenceHashcode(V vertex, Graph context)
{
InOutDegrees inOut = getInOutDegrees(context, vertex);
// hash it using the string hash. use the format N '-' N
StringBuffer sb = new StringBuffer();
sb.append(String.valueOf(inOut.inDegree));
sb.append("-"); // to diffrentiate inner and outer
sb.append(String.valueOf(inOut.outDegree));
return sb.toString().hashCode();
}
/**
* Calculates the In and Out degrees of vertexes. Supported graph types:
* UnDirectedGraph, DirectedGraph. In UnDirected graph, the in = out (as if
* it was undirected and every edge is both an in and out edge)
*
* @param aContextGraph
* @param vertex
*/
protected InOutDegrees getInOutDegrees(Graph aContextGraph,
V vertex)
{
int inVertexDegree = 0;
int outVertexDegree = 0;
if (aContextGraph instanceof UndirectedGraph) {
UndirectedGraph undirectedGraph =
(UndirectedGraph) aContextGraph;
inVertexDegree = undirectedGraph.degreeOf(vertex);
outVertexDegree = inVertexDegree; // it is UNdirected
} else if (aContextGraph instanceof DirectedGraph) {
DirectedGraph directedGraph =
(DirectedGraph) aContextGraph;
inVertexDegree = directedGraph.inDegreeOf(vertex);
outVertexDegree = directedGraph.outDegreeOf(vertex);
} else {
throw new RuntimeException(
"contextGraph is of unsupported type . It must be one of these two :"
+ " UndirectedGraph or DirectedGraph");
}
return new InOutDegrees(inVertexDegree, outVertexDegree);
}
/**
* Simple structure used to hold the two ints: vertex in degree and vertex
* out degree. Useful as returned value for methods which calculate both at
* the same time.
*
* @author Assaf
* @since Jul 21, 2005
*/
protected class InOutDegrees
{
public int inDegree;
public int outDegree;
public InOutDegrees(int aInDegree, int aOutDegree)
{
this.inDegree = aInDegree;
this.outDegree = aOutDegree;
}
/**
* Checks both inDegree and outDegree. Does not check class type to save
* time. If should be used with caution.
*
* @see java.lang.Object#equals(java.lang.Object)
*/
@Override public boolean equals(Object obj)
{
InOutDegrees other = (InOutDegrees) obj;
return ((this.inDegree == other.inDegree)
&& (this.outDegree == other.outDegree));
}
}
}
// End VertexDegreeEquivalenceComparator.java