scratch.joshua.jung_2_0.core.SimpleUndirectedSparseGraph.java Source code

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Here is the source code for scratch.joshua.jung_2_0.core.SimpleUndirectedSparseGraph.java

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/*
 * Created on Oct 18, 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 scratch.joshua.jung_2_0.core;

import java.util.Collection;
import java.util.HashMap;
import java.util.HashSet;
import java.util.Map;
import java.util.Set;

import org.apache.commons.collections.CollectionUtils;

import scratch.joshua.jung_2_0.utils.Pair;

public class SimpleUndirectedSparseGraph<V, E> extends SimpleAbstractSparseGraph<V, E>
        implements UndirectedGraph<V, E> {
    protected Map<V, Set<E>> vertices; // Map of vertices to adjacency sets
    protected Map<E, Pair<V>> edges; // Map of edges to incident vertex sets

    public SimpleUndirectedSparseGraph() {
        vertices = new HashMap();
        edges = new HashMap();
    }

    public Collection<E> getEdges() {
        return CollectionUtils.unmodifiableCollection(edges.keySet());
    }

    public Collection<V> getVertices() {
        return CollectionUtils.unmodifiableCollection(vertices.keySet());
    }

    public boolean addVertex(V vertex) {
        if (!vertices.containsKey(vertex)) {
            vertices.put(vertex, new HashSet<E>());
            return true;
        } else
            return false;
    }

    public boolean removeVertex(V vertex) {
        Set<E> adj_set = vertices.remove(vertex);
        if (adj_set == null)
            return false;

        for (E edge : adj_set)
            removeEdge(edge);

        return true;
    }

    public boolean addUndirectedEdge(E edge, V v1, V v2) {
        if (edges.containsKey(edge))
            return false;

        Pair<V> endpoints = new Pair(v1, v2);
        edges.put(edge, endpoints);
        vertices.get(v1).add(edge);
        vertices.get(v2).add(edge);

        return true;
    }

    public boolean removeEdge(E edge) {
        if (!edges.containsKey(edge))
            return false;

        Pair<V> endpoints = getEndpoints(edge);
        V v1 = endpoints.getFirst();
        V v2 = endpoints.getSecond();

        // remove edge from incident vertices' adjacency sets
        vertices.get(v1).remove(edge);
        vertices.get(v2).remove(edge);

        edges.remove(edge);
        return true;
    }

    public Collection<E> getInEdges(V vertex) {
        return this.getIncidentEdges(vertex);
    }

    public Collection<E> getOutEdges(V vertex) {
        return this.getIncidentEdges(vertex);
    }

    public Collection<V> getPredecessors(V vertex) {
        return this.getNeighbors(vertex);
    }

    public Collection<V> getSuccessors(V vertex) {
        return this.getNeighbors(vertex);
    }

    public Collection<V> getNeighbors(V vertex) {
        Set<E> incident_edges = vertices.get(vertex);
        Set<V> neighbors = new HashSet<V>();
        for (E edge : incident_edges) {
            Pair<V> endpoints = this.getEndpoints(edge);
            V e_a = endpoints.getFirst();
            V e_b = endpoints.getSecond();
            if (vertex.equals(e_a))
                neighbors.add(e_b);
            else
                neighbors.add(e_a);
        }

        return CollectionUtils.unmodifiableCollection(neighbors);
    }

    public Collection<E> getIncidentEdges(V vertex) {
        return CollectionUtils.unmodifiableCollection((Set) vertices.get(vertex));
    }

    public E findEdge(V v1, V v2) {
        Set<E> incident_edges = vertices.get(v1);
        for (E edge : incident_edges) {
            Pair<V> endpoints = this.getEndpoints(edge);
            V e_a = endpoints.getFirst();
            V e_b = endpoints.getSecond();
            if ((v1.equals(e_a) && v2.equals(e_b)) || (v1.equals(e_b) && v2.equals(e_a)))
                return edge;
        }

        return null;
    }

    public Pair<V> getEndpoints(E edge) {
        return edges.get(edge);
    }
}