320 lines
11 KiB
Java
320 lines
11 KiB
Java
package graph;
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/**
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* Created with xgiovio.macbookair.
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* User: xgiovio
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* Date: 19/05/14
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* Time: 16:30
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*/
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import java.util.Iterator;
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/**
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* An realization of a graph according to adjacency list structure.
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*
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* @author Roberto Tamassia, Eric Zamore
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*/
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public class AdjacencyListGraph<V,E> implements Graph<V,E> {
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protected NodePositionList<Vertex<V>> VList; // container for vertices
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protected NodePositionList<Edge<E>> EList; // container for edges
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/** Default constructor that creates an empty graph */
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public AdjacencyListGraph() {
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VList = new NodePositionList<Vertex<V>>();
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EList = new NodePositionList<Edge<E>>();
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}
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/** Return an iterator over the vertices of the graph */
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public Iterable<Vertex<V>> vertices() {
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return VList;
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}
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/** Return an iterator over the edges of the graph */
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public Iterable<Edge<E>> edges() {
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return EList;
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}
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/** Replace the element a given position (vertex or edge) with a new
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element and return the old element */
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public Object replace(Position p, Object o)
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throws InvalidPositionException {
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MyPosition pp = checkPosition(p);
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Object temp = p.element();
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pp.setElement(o);
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return temp;
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}
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/** Return an iterator over the edges incident on a vertex */
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public Iterable<Edge<E>> incidentEdges(Vertex<V> v)
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throws InvalidPositionException {
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MyVertex<V> vv = checkVertex(v);
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return vv.incidentEdges();
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}
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/** Return the endvertices of a edge in an array of length 2 */
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public Vertex<V>[] endVertices(Edge<E> e)
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throws InvalidPositionException {
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MyEdge<E> ee = checkEdge(e);
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return ee.endVertices();
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}
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/** Return the other endvertex of an incident edge */
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public Vertex<V> opposite(Vertex<V> v, Edge<E> e)
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throws InvalidPositionException {
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checkVertex(v);
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MyEdge<E> ee = checkEdge(e);
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Vertex<V>[] endv = ee.endVertices();
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if (v == endv[0])
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return endv[1];
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else if (v == endv[1])
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return endv[0];
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else
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throw new InvalidPositionException("No such vertex exists");
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}
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/** Test whether two vertices are adjacent */
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public boolean areAdjacent(Vertex<V> u, Vertex<V> v)
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throws InvalidPositionException {
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// search the incidence list of the vertex with smaller degree
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Iterable<Edge<E>> iterToSearch;
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if (degree(u) < degree(v)) {
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iterToSearch = incidentEdges(u);
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}
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else {
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iterToSearch = incidentEdges(v);
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}
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for (Edge<E> e: iterToSearch ) {
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Vertex<V>[] endV = endVertices(e);
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// if there exists an edge whose endpoints are u and v
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if ((endV[0] == u && endV[1] == v) || (endV[0] == v && endV[1] == u))
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return true;
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}
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return false;
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}
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/** Insert and return a new vertex with a given element */
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public Vertex<V> insertVertex(V o) {
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MyVertex<V> vv = new MyVertex<V>(o);
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VList.addLast(vv);
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Position<Vertex<V>> p = VList.last();
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vv.setLocation(p);
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return vv;
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}
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/** Insert and return a new edge with a given element between two
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vertices */
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public Edge<E> insertEdge(Vertex<V> v, Vertex<V> w, E o)
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throws InvalidPositionException {
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MyVertex<V> vv = checkVertex(v);
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MyVertex<V> ww = checkVertex(w);
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MyEdge<E> ee = new MyEdge<E>(v, w, o);
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Position<Edge<E>> pv = vv.insertIncidence(ee);
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Position<Edge<E>> pw = ww.insertIncidence(ee);
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ee.setIncidences(pv, pw);
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EList.addLast(ee);
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Position<Edge<E>> pe = EList.last();
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ee.setLocation(pe);
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return ee;
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}
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/** Remove a vertex and all its incident edges and return the
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element stored at the removed vertex */
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public V removeVertex(Vertex<V> v)
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throws InvalidPositionException {
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MyVertex<V> vv = checkVertex(v);
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Iterator<Edge<E>> inc = incidentEdges(v).iterator();
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while (inc.hasNext()) {
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MyEdge<E> e = (MyEdge<E>) inc.next();
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if (e.location() != null) // if the edge has not been marked invalid
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removeEdge(e);
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}
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VList.remove(vv.location());
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return v.element();
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}
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/** Remove an edge and return its element */
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public E removeEdge(Edge<E> e)
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throws InvalidPositionException {
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MyEdge<E> ee = checkEdge(e);
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MyVertex<V>[] endv = ee.endVertices();
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Position<Edge<E>>[] inc = ee.incidences();
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endv[0].removeIncidence(inc[0]);
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endv[1].removeIncidence(inc[1]);
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EList.remove(ee.location());
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ee.setLocation(null); // invalidating this edge
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return e.element();
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}
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// Auxiliary methods
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/** Return the degree of a given vertex */
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public int degree(Vertex<V> v) {
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MyVertex<V> vv = checkVertex(v);
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return vv.degree();
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}
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/** Determines whether a given position is valid. */
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protected MyPosition checkPosition(Position p)
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throws InvalidPositionException {
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if (p == null || !(p instanceof MyPosition))
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throw new InvalidPositionException("Position is invalid");
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return (MyPosition) p;
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}
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/** Determines whether a given vertex is valid. */
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protected MyVertex<V> checkVertex(Vertex<V> v)
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throws InvalidPositionException {
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if (v == null || !(v instanceof MyVertex))
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throw new InvalidPositionException("Vertex is invalid");
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return (MyVertex<V>) v;
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}
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/** Determines whether a given edge is valid. */
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protected MyEdge<E> checkEdge(Edge<E> e)
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throws InvalidPositionException {
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if (e == null || !(e instanceof MyEdge))
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throw new InvalidPositionException("Edge is invalid");
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return (MyEdge<E>) e;
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}
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/** Implementation of a decorable position by means of a hash
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* table. */
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protected static class MyPosition<T>
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extends HashTableMap<Object,Object> implements DecorablePosition<T> {
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/** The element stored at this position. */
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protected T elem;
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/** Returns the element stored at this position. */
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public T element() {
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return elem;
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}
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/** Sets the element stored at this position. */
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public void setElement(T o) {
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elem = o;
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}
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}
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/** Returns a string representation of the vertex and edge lists,
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* separated by a newline. */
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public String toString() {
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return VList.toString() + "\n" + EList.toString();
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}
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public int numVertices() {
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return VList.size();
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}
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public int numEdges() {
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return EList.size();
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}
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public V replace(Vertex<V> p, V o) throws InvalidPositionException {
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V temp = p.element();
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MyVertex<V> vv = checkVertex(p);
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vv.setElement(o);
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return temp;
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}
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public E replace(Edge<E> p, E o) throws InvalidPositionException {
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E temp = p.element();
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MyEdge<E> ee = checkEdge(p);
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ee.setElement(o);
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return temp;
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}
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/** Implementation of a vertex for an undirected adjacency list
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* graph. Each vertex stores its incidence container and position
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* in the vertex container of the graph. */
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protected class MyVertex<V>
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extends MyPosition<V> implements Vertex<V> {
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/** Incidence container of the vertex. */
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protected PositionList<Edge<E>> incEdges;
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/** Position of the vertex in the vertex container of the graph. */
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protected Position<Vertex<V>> loc;
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/** Constructs the vertex with the given element. */
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MyVertex(V o) {
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elem = o;
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incEdges = new NodePositionList<Edge<E>>();
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}
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/** Return the degree of a given vertex */
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public int degree() {
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return incEdges.size();
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}
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/** Returns the incident edges on this vertex. */
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public Iterable<Edge<E>> incidentEdges() {
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return incEdges;
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}
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/** Inserts an edge into the incidence container of this vertex. */
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public Position<Edge<E>> insertIncidence(Edge<E> e) {
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incEdges.addLast(e);
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return incEdges.last();
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}
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/** Removes an edge from the incidence container of this vertex. */
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public void removeIncidence(Position<Edge<E>> p) {
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incEdges.remove(p);
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}
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/** Returns the position of this vertex in the vertex container of
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* the graph. */
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public Position<Vertex<V>> location() {
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return loc;
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}
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/** Sets the position of this vertex in the vertex container of
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* the graph. */
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public void setLocation(Position<Vertex<V>> p) {
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loc = p;
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}
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/** Returns a string representation of the element stored at this
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* vertex. */
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public String toString() {
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return elem.toString();
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}
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}
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/** Implementation of an edge for an undirected adjacency list
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* graph. Each edge stores its endpoints (end vertices), its
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* positions within the incidence containers of its endpoints, and
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* position in the edge container of the graph. */
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protected class MyEdge<E> extends MyPosition<E> implements Edge<E> {
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/** The end vertices of the edge. */
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protected MyVertex<V>[] endVertices;
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/** The positions of the entries for the edge in the incidence
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* containers of the end vertices. */
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protected Position<Edge<E>>[] Inc;
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/** The position of the edge in the edge container of the
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* graph. */
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protected Position<Edge<E>> loc;
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/** Constructs an edge with the given endpoints and elements. */
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MyEdge (Vertex<V> v, Vertex<V> w, E o) {
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elem = o;
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endVertices = (MyVertex<V>[]) new MyVertex[2];
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endVertices[0] = (MyVertex<V>)v;
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endVertices[1] = (MyVertex<V>)w;
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Inc = (Position<Edge<E>>[]) new Position[2];
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}
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/** Returns the end vertices of the edge. There are always two
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* elements in the returned array. */
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public MyVertex<V>[] endVertices() {
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return endVertices;
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}
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/** Returns the positions of the edge in the incidence containers
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* of its end vertices. The returned array always contains two
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* elements. */
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public Position<Edge<E>>[] incidences() {
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return Inc;
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}
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/** Sets the positions of the edge in the incidence containers of
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* its end vertices. */
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public void setIncidences(Position<Edge<E>> pv, Position<Edge<E>> pw) {
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Inc[0] = pv;
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Inc[1] = pw;
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}
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/** Returns the position of the edge in the edge container of the
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* graph. */
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public Position<Edge<E>> location() {
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return loc;
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}
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/** Sets the position of the edge in the edge container of the
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* graph. */
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public void setLocation(Position<Edge<E>> p) {
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loc = p;
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}
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/** Returns a string representation of the edge via a tuple of
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* vertices. */
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public String toString() {
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return element() + "(" + endVertices[0].toString() +
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"," + endVertices[1].toString() + ")";
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}
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}
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} |