/* ==========================================
* 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.
*/
/* ------------------
* AbstractGraph.java
* ------------------
* (C) Copyright 2003-2008, by Barak Naveh and Contributors.
*
* Original Author: Barak Naveh
* Contributor(s): Christian Hammer
* Vladimir Kostyukov
*
* $Id$
*
* Changes
* -------
* 24-Jul-2003 : Initial revision (BN);
* 11-Mar-2004 : Made generic (CH);
* 07-May-2006 : Changed from List<Edge> to Set<Edge> (JVS);
* 28-May-2006 : Moved connectivity info from edge to graph (JVS);
* 14-Jun-2012 : Added hashCode() and equals() methods implementation (VK);
*
*/
package org.jgrapht.graph;
import java.util.*;
import org.jgrapht.*;
import org.jgrapht.util.*;
/**
* A skeletal implementation of the <tt>Graph</tt> interface, to minimize the
* effort required to implement graph interfaces. This implementation is
* applicable to both: directed graphs and undirected graphs.
*
* @author Barak Naveh
* @see Graph
* @see DirectedGraph
* @see UndirectedGraph
*/
public abstract class AbstractGraph<V, E>
implements Graph<V, E>
{
/**
* Construct a new empty graph object.
*/
public AbstractGraph()
{
}
/**
* @see Graph#containsEdge(Object, Object)
*/
public boolean containsEdge(V sourceVertex, V targetVertex)
{
return getEdge(sourceVertex, targetVertex) != null;
}
/**
* @see Graph#removeAllEdges(Collection)
*/
public boolean removeAllEdges(Collection<? extends E> edges)
{
boolean modified = false;
for (E e : edges) {
modified |= removeEdge(e);
}
return modified;
}
/**
* @see Graph#removeAllEdges(Object, Object)
*/
public Set<E> removeAllEdges(V sourceVertex, V targetVertex)
{
Set<E> removed = getAllEdges(sourceVertex, targetVertex);
if (removed == null) {
return null;
}
removeAllEdges(removed);
return removed;
}
/**
* @see Graph#removeAllVertices(Collection)
*/
public boolean removeAllVertices(Collection<? extends V> vertices)
{
boolean modified = false;
for (V v : vertices) {
modified |= removeVertex(v);
}
return modified;
}
/**
* Returns a string of the parenthesized pair (V, E) representing this
* G=(V,E) graph. 'V' is the string representation of the vertex set, and
* 'E' is the string representation of the edge set.
*
* @return a string representation of this graph.
*/
public String toString()
{
return toStringFromSets(
vertexSet(),
edgeSet(),
(this instanceof DirectedGraph<?, ?>));
}
/**
* Ensures that the specified vertex exists in this graph, or else throws
* exception.
*
* @param v vertex
*
* @return <code>true</code> if this assertion holds.
*
* @throws NullPointerException if specified vertex is <code>null</code>.
* @throws IllegalArgumentException if specified vertex does not exist in
* this graph.
*/
protected boolean assertVertexExist(V v)
{
if (containsVertex(v)) {
return true;
} else if (v == null) {
throw new NullPointerException();
} else {
throw new IllegalArgumentException("no such vertex in graph");
}
}
/**
* Removes all the edges in this graph that are also contained in the
* specified edge array. After this call returns, this graph will contain no
* edges in common with the specified edges. This method will invoke the
* {@link Graph#removeEdge(Object)} method.
*
* @param edges edges to be removed from this graph.
*
* @return <tt>true</tt> if this graph changed as a result of the call.
*
* @see Graph#removeEdge(Object)
* @see Graph#containsEdge(Object)
*/
protected boolean removeAllEdges(E [] edges)
{
boolean modified = false;
for (int i = 0; i < edges.length; i++) {
modified |= removeEdge(edges[i]);
}
return modified;
}
/**
* Helper for subclass implementations of toString( ).
*
* @param vertexSet the vertex set V to be printed
* @param edgeSet the edge set E to be printed
* @param directed true to use parens for each edge (representing directed);
* false to use curly braces (representing undirected)
*
* @return a string representation of (V,E)
*/
protected String toStringFromSets(
Collection<? extends V> vertexSet,
Collection<? extends E> edgeSet,
boolean directed)
{
List<String> renderedEdges = new ArrayList<String>();
StringBuffer sb = new StringBuffer();
for (E e : edgeSet) {
if ((e.getClass() != DefaultEdge.class)
&& (e.getClass() != DefaultWeightedEdge.class))
{
sb.append(e.toString());
sb.append("=");
}
if (directed) {
sb.append("(");
} else {
sb.append("{");
}
sb.append(getEdgeSource(e));
sb.append(",");
sb.append(getEdgeTarget(e));
if (directed) {
sb.append(")");
} else {
sb.append("}");
}
// REVIEW jvs 29-May-2006: dump weight somewhere?
renderedEdges.add(sb.toString());
sb.setLength(0);
}
return "(" + vertexSet + ", " + renderedEdges + ")";
}
/**
* Returns a hash code value for this graph. The hash code of a graph is
* defined to be the sum of the hash codes of vertices and edges in the
* graph. It is also based on graph topology and edges weights.
*
* @return the hash code value this graph
*
* @see Object#hashCode()
*/
public int hashCode()
{
int hash = vertexSet().hashCode();
for (E e : edgeSet()) {
int part = e.hashCode();
int source = getEdgeSource(e).hashCode();
int target = getEdgeTarget(e).hashCode();
// see http://en.wikipedia.org/wiki/Pairing_function (VK);
int pairing =
((source + target)
* (source + target + 1) / 2) + target;
part = (27 * part) + pairing;
long weight = (long) getEdgeWeight(e);
part = (27 * part) + (int) (weight ^ (weight >>> 32));
hash += part;
}
return hash;
}
/**
* Indicates whether some other object is "equal to" this graph. Returns
* <code>true</code> if the given object is also a graph, the two graphs are
* instances of the same graph class, have identical vertices and edges sets
* with the same weights.
*
* @param obj object to be compared for equality with this graph
*
* @return <code>true</code> if the specified object is equal to this graph
*
* @see Object#equals(Object)
*/
public boolean equals(Object obj)
{
if (this == obj) {
return true;
}
if ((obj == null) || (getClass() != obj.getClass())) {
return false;
}
TypeUtil<Graph<V, E>> typeDecl = null;
Graph<V, E> g = TypeUtil.uncheckedCast(obj, typeDecl);
if (!vertexSet().equals(g.vertexSet())) {
return false;
}
if (edgeSet().size() != g.edgeSet().size()) {
return false;
}
for (E e : edgeSet()) {
V source = getEdgeSource(e);
V target = getEdgeTarget(e);
if (!g.containsEdge(e)) {
return false;
}
if (!g.getEdgeSource(e).equals(source)
|| !g.getEdgeTarget(e).equals(target))
{
return false;
}
if (Math.abs(getEdgeWeight(e) - g.getEdgeWeight(e)) > 10e-7) {
return false;
}
}
return true;
}
}
// End AbstractGraph.java