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/*
* (C) Copyright 2015-2023, by Joris Kinable and Contributors.
*
* JGraphT : a free Java graph-theory library
*
* See the CONTRIBUTORS.md file distributed with this work for additional
* information regarding copyright ownership.
*
* This program and the accompanying materials are made available under the
* terms of the Eclipse Public License 2.0 which is available at
* http://www.eclipse.org/legal/epl-2.0, or the
* GNU Lesser General Public License v2.1 or later
* which is available at
* http://www.gnu.org/licenses/old-licenses/lgpl-2.1-standalone.html.
*
* SPDX-License-Identifier: EPL-2.0 OR LGPL-2.1-or-later
*/
package org.jgrapht.graph.specifics;
import org.jgrapht.*;
import org.jgrapht.alg.util.*;
import org.jgrapht.graph.*;
import java.util.*;
import java.util.function.*;
/**
* Fast implementation of UndirectedSpecifics. This class uses additional data structures to improve
* the performance of methods which depend on edge retrievals, e.g. getEdge(V u, V v),
* containsEdge(V u, V v), addEdge(V u, V v). A disadvantage is an increase in memory consumption.
* If memory utilization is an issue, use a {@link UndirectedSpecifics} instead.
*
* @param the graph vertex type
* @param the graph edge type
*
* @author Joris Kinable
*/
public class FastLookupUndirectedSpecifics
extends UndirectedSpecifics
{
private static final long serialVersionUID = 225772727571597846L;
/**
* Maps a pair of vertices <u,v> to a set of edges {(u,v)}. In case of a multigraph, all
* edges which touch both u and v are included in the set.
*/
protected Map, Set> touchingVerticesToEdgeMap;
/**
* Construct a new fast lookup undirected specifics.
*
* @param graph the graph for which these specifics are for
* @param vertexMap map for the storage of vertex edge sets. Needs to have a predictable
* iteration order.
* @param touchingVerticesToEdgeMap Additional map for caching. No need for a predictable
* iteration order.
* @param edgeSetFactory factory for the creation of vertex edge sets
*/
public FastLookupUndirectedSpecifics(
Graph graph, Map> vertexMap,
Map, Set> touchingVerticesToEdgeMap, EdgeSetFactory edgeSetFactory)
{
super(graph, vertexMap, edgeSetFactory);
this.touchingVerticesToEdgeMap = Objects.requireNonNull(touchingVerticesToEdgeMap);
}
@Override
public Set getAllEdges(V sourceVertex, V targetVertex)
{
if (graph.containsVertex(sourceVertex) && graph.containsVertex(targetVertex)) {
Set edges =
touchingVerticesToEdgeMap.get(new UnorderedPair<>(sourceVertex, targetVertex));
if (edges == null) {
return Collections.emptySet();
} else {
Set edgeSet = edgeSetFactory.createEdgeSet(sourceVertex);
edgeSet.addAll(edges);
return edgeSet;
}
} else {
return null;
}
}
@Override
public E getEdge(V sourceVertex, V targetVertex)
{
Set edges =
touchingVerticesToEdgeMap.get(new UnorderedPair<>(sourceVertex, targetVertex));
if (edges == null || edges.isEmpty())
return null;
else
return edges.iterator().next();
}
@Override
public boolean addEdgeToTouchingVertices(V sourceVertex, V targetVertex, E e)
{
if (!super.addEdgeToTouchingVertices(sourceVertex, targetVertex, e)) {
return false;
}
addToIndex(sourceVertex, targetVertex, e);
return true;
}
@Override
public boolean addEdgeToTouchingVerticesIfAbsent(V sourceVertex, V targetVertex, E e)
{
// first lookup using our own index
E edge = getEdge(sourceVertex, targetVertex);
if (edge != null) {
return false;
}
return addEdgeToTouchingVertices(sourceVertex, targetVertex, e);
}
@Override
public E createEdgeToTouchingVerticesIfAbsent(
V sourceVertex, V targetVertex, Supplier edgeSupplier)
{
// first lookup using our own index
E edge = getEdge(sourceVertex, targetVertex);
if (edge != null) {
return null;
}
E e = edgeSupplier.get();
addEdgeToTouchingVertices(sourceVertex, targetVertex, e);
return e;
}
@Override
public void removeEdgeFromTouchingVertices(V sourceVertex, V targetVertex, E e)
{
super.removeEdgeFromTouchingVertices(sourceVertex, targetVertex, e);
removeFromIndex(sourceVertex, targetVertex, e);
}
/**
* Add an edge to the index.
*
* @param sourceVertex the source vertex
* @param targetVertex the target vertex
* @param e the edge
*/
protected void addToIndex(V sourceVertex, V targetVertex, E e)
{
Pair vertexPair = new UnorderedPair<>(sourceVertex, targetVertex);
Set edgeSet = touchingVerticesToEdgeMap.get(vertexPair);
if (edgeSet != null)
edgeSet.add(e);
else {
edgeSet = edgeSetFactory.createEdgeSet(sourceVertex);
edgeSet.add(e);
touchingVerticesToEdgeMap.put(vertexPair, edgeSet);
}
}
/**
* Remove an edge from the index.
*
* @param sourceVertex the source vertex
* @param targetVertex the target vertex
* @param e the edge
*/
protected void removeFromIndex(V sourceVertex, V targetVertex, E e)
{
Pair vertexPair = new UnorderedPair<>(sourceVertex, targetVertex);
Set edgeSet = touchingVerticesToEdgeMap.get(vertexPair);
if (edgeSet != null) {
edgeSet.remove(e);
if (edgeSet.isEmpty())
touchingVerticesToEdgeMap.remove(vertexPair);
}
}
}