Java tutorial
/* * Copyright (c) 2003, 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. */ /* * Created on Apr 21, 2004 */ package edu.uci.ics.jung.algorithms.transformation; import java.util.ArrayList; import java.util.Collection; import org.apache.commons.collections15.Factory; import org.apache.commons.collections15.Predicate; import edu.uci.ics.jung.graph.Graph; import edu.uci.ics.jung.graph.Hypergraph; import edu.uci.ics.jung.graph.KPartiteGraph; /** * Methods for creating a "folded" graph based on a k-partite graph or a * hypergraph. * * <p>A "folded" graph is derived from a k-partite graph by identifying * a partition of vertices which will become the vertices of the new graph, copying * these vertices into the new graph, and then connecting those vertices whose * original analogues were connected indirectly through elements * of other partitions.</p> * * <p>A "folded" graph is derived from a hypergraph by creating vertices based on * either the vertices or the hyperedges of the original graph, and connecting * vertices in the new graph if their corresponding vertices/hyperedges share a * connection with a common hyperedge/vertex.</p> * * @author Danyel Fisher * @author Joshua O'Madadhain */ public class FoldingTransformer<V, E> { /** * Converts <code>g</code> into a unipartite graph whose vertex set is the * vertices of <code>g</code>'s partition <code>p</code>. For vertices * <code>a</code> and <code>b</code> in this partition, the resultant * graph will include the edge <code>(a,b)</code> if the original graph * contains edges <code>(a,c)</code> and <code>(c,b)</code> for at least * one vertex <code>c</code>. * * <p>The vertices of the new graph are the same as the vertices of the * appropriate partition in the old graph; the edges in the new graph are * created by the input edge <code>Factory</code>.</p> * * <p>If there is more than 1 such vertex <code>c</code> for a given pair * <code>(a,b)</code>, the type of the output graph will determine whether * it will contain parallel edges or not.</p> * * <p>This function will not create self-loops.</p> * * @param <V> vertex type * @param <E> input edge type * @param g input k-partite graph * @param p predicate specifying vertex partition * @param graph_factory factory used to create the output graph * @param edge_factory factory used to create the edges in the new graph * @return a copy of the input graph folded with respect to the input partition */ public static <V, E> Graph<V, E> foldKPartiteGraph(KPartiteGraph<V, E> g, Predicate<V> p, Factory<Graph<V, E>> graph_factory, Factory<E> edge_factory) { Graph<V, E> newGraph = graph_factory.create(); // get vertices for the specified partition Collection<V> vertices = g.getVertices(p); for (V v : vertices) { newGraph.addVertex(v); for (V s : g.getSuccessors(v)) { for (V t : g.getSuccessors(s)) { if (!vertices.contains(t) || t.equals(v)) continue; newGraph.addVertex(t); newGraph.addEdge(edge_factory.create(), v, t); } } } return newGraph; } /** * Converts <code>g</code> into a unipartite graph whose vertices are the * vertices of <code>g</code>'s partition <code>p</code>, and whose edges * consist of collections of the intermediate vertices from other partitions. * For vertices * <code>a</code> and <code>b</code> in this partition, the resultant * graph will include the edge <code>(a,b)</code> if the original graph * contains edges <code>(a,c)</code> and <code>(c,b)</code> for at least * one vertex <code>c</code>. * * <p>The vertices of the new graph are the same as the vertices of the * appropriate partition in the old graph; the edges in the new graph are * collections of the intermediate vertices <code>c</code>.</p> * * <p>This function will not create self-loops.</p> * * @param <V> vertex type * @param <E> input edge type * @param g input k-partite graph * @param p predicate specifying vertex partition * @param graph_factory factory used to create the output graph * @return the result of folding g into unipartite graph whose vertices * are those of the <code>p</code> partition of g */ public static <V, E> Graph<V, Collection<V>> foldKPartiteGraph(KPartiteGraph<V, E> g, Predicate<V> p, Factory<Graph<V, Collection<V>>> graph_factory) { Graph<V, Collection<V>> newGraph = graph_factory.create(); // get vertices for the specified partition, copy into new graph Collection<V> vertices = g.getVertices(p); for (V v : vertices) { newGraph.addVertex(v); for (V s : g.getSuccessors(v)) { for (V t : g.getSuccessors(s)) { if (!vertices.contains(t) || t.equals(v)) continue; newGraph.addVertex(t); Collection<V> v_coll = newGraph.findEdge(v, t); if (v_coll == null) { v_coll = new ArrayList<V>(); newGraph.addEdge(v_coll, v, t); } v_coll.add(s); } } } return newGraph; } /** * Creates a <code>Graph</code> which is an edge-folded version of <code>h</code>, where * hyperedges are replaced by k-cliques in the output graph. * * <p>The vertices of the new graph are the same objects as the vertices of * <code>h</code>, and <code>a</code> * is connected to <code>b</code> in the new graph if the corresponding vertices * in <code>h</code> are connected by a hyperedge. Thus, each hyperedge with * <i>k</i> vertices in <code>h</code> induces a <i>k</i>-clique in the new graph.</p> * * <p>The edges of the new graph consist of collections of each hyperedge that connected * the corresponding vertex pair in the original graph.</p> * * @param <V> vertex type * @param <E> input edge type * @param h hypergraph to be folded * @param graph_factory factory used to generate the output graph * @return a copy of the input graph where hyperedges are replaced by cliques */ public static <V, E> Graph<V, Collection<E>> foldHypergraphEdges(Hypergraph<V, E> h, Factory<Graph<V, Collection<E>>> graph_factory) { Graph<V, Collection<E>> target = graph_factory.create(); for (V v : h.getVertices()) target.addVertex(v); for (E e : h.getEdges()) { ArrayList<V> incident = new ArrayList<V>(h.getIncidentVertices(e)); populateTarget(target, e, incident); } return target; } /** * Creates a <code>Graph</code> which is an edge-folded version of <code>h</code>, where * hyperedges are replaced by k-cliques in the output graph. * * <p>The vertices of the new graph are the same objects as the vertices of * <code>h</code>, and <code>a</code> * is connected to <code>b</code> in the new graph if the corresponding vertices * in <code>h</code> are connected by a hyperedge. Thus, each hyperedge with * <i>k</i> vertices in <code>h</code> induces a <i>k</i>-clique in the new graph.</p> * * <p>The edges of the new graph are generated by the specified edge factory.</p> * * @param <V> vertex type * @param <E> input edge type * @param h hypergraph to be folded * @param graph_factory factory used to generate the output graph * @param edge_factory factory used to create the new edges * @return a copy of the input graph where hyperedges are replaced by cliques */ public static <V, E> Graph<V, E> foldHypergraphEdges(Hypergraph<V, E> h, Factory<Graph<V, E>> graph_factory, Factory<E> edge_factory) { Graph<V, E> target = graph_factory.create(); for (V v : h.getVertices()) target.addVertex(v); for (E e : h.getEdges()) { ArrayList<V> incident = new ArrayList<V>(h.getIncidentVertices(e)); for (int i = 0; i < incident.size(); i++) for (int j = i + 1; j < incident.size(); j++) target.addEdge(edge_factory.create(), incident.get(i), incident.get(j)); } return target; } /** * Creates a <code>Graph</code> which is a vertex-folded version of <code>h</code>, whose * vertices are the input's hyperedges and whose edges are induced by adjacent hyperedges * in the input. * * <p>The vertices of the new graph are the same objects as the hyperedges of * <code>h</code>, and <code>a</code> * is connected to <code>b</code> in the new graph if the corresponding edges * in <code>h</code> have a vertex in common. Thus, each vertex incident to * <i>k</i> edges in <code>h</code> induces a <i>k</i>-clique in the new graph.</p> * * <p>The edges of the new graph are created by the specified factory.</p> * * @param <V> vertex type * @param <E> input edge type * @param <F> output edge type * @param h hypergraph to be folded * @param graph_factory factory used to generate the output graph * @param edge_factory factory used to generate the output edges * @return a transformation of the input graph whose vertices correspond to the input's hyperedges * and edges are induced by hyperedges sharing vertices in the input */ public static <V, E, F> Graph<E, F> foldHypergraphVertices(Hypergraph<V, E> h, Factory<Graph<E, F>> graph_factory, Factory<F> edge_factory) { Graph<E, F> target = graph_factory.create(); for (E e : h.getEdges()) target.addVertex(e); for (V v : h.getVertices()) { ArrayList<E> incident = new ArrayList<E>(h.getIncidentEdges(v)); for (int i = 0; i < incident.size(); i++) for (int j = i + 1; j < incident.size(); j++) target.addEdge(edge_factory.create(), incident.get(i), incident.get(j)); } return target; } /** * Creates a <code>Graph</code> which is a vertex-folded version of <code>h</code>, whose * vertices are the input's hyperedges and whose edges are induced by adjacent hyperedges * in the input. * * <p>The vertices of the new graph are the same objects as the hyperedges of * <code>h</code>, and <code>a</code> * is connected to <code>b</code> in the new graph if the corresponding edges * in <code>h</code> have a vertex in common. Thus, each vertex incident to * <i>k</i> edges in <code>h</code> induces a <i>k</i>-clique in the new graph.</p> * * <p>The edges of the new graph consist of collections of each vertex incident to * the corresponding hyperedge pair in the original graph.</p> * * @param h hypergraph to be folded * @param graph_factory factory used to generate the output graph * @return a transformation of the input graph whose vertices correspond to the input's hyperedges * and edges are induced by hyperedges sharing vertices in the input */ public Graph<E, Collection<V>> foldHypergraphVertices(Hypergraph<V, E> h, Factory<Graph<E, Collection<V>>> graph_factory) { Graph<E, Collection<V>> target = graph_factory.create(); for (E e : h.getEdges()) target.addVertex(e); for (V v : h.getVertices()) { ArrayList<E> incident = new ArrayList<E>(h.getIncidentEdges(v)); populateTarget(target, v, incident); } return target; } /** * @param target * @param e * @param incident */ private static <S, T> void populateTarget(Graph<S, Collection<T>> target, T e, ArrayList<S> incident) { for (int i = 0; i < incident.size(); i++) { S v1 = incident.get(i); for (int j = i + 1; j < incident.size(); j++) { S v2 = incident.get(j); Collection<T> e_coll = target.findEdge(v1, v2); if (e_coll == null) { e_coll = new ArrayList<T>(); target.addEdge(e_coll, v1, v2); } e_coll.add(e); } } } }