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/*******************************************************************************
* Copyright (c) 2010-2012, Tamas Szabo, Istvan Rath and Daniel Varro
* This program and the accompanying materials are made available under the
* terms of the Eclipse Public License v. 2.0 which is available at
* http://www.eclipse.org/legal/epl-v20.html.
*
* SPDX-License-Identifier: EPL-2.0
*******************************************************************************/
package tools.refinery.viatra.runtime.rete.itc.alg.misc.bfs;
import tools.refinery.viatra.runtime.rete.itc.igraph.IBiDirectionalGraphDataSource;
import tools.refinery.viatra.runtime.rete.itc.igraph.IGraphDataSource;
import java.util.*;
public class BFS<V> {
private BFS() {/*Utility class constructor*/}
/**
* Performs a breadth first search on the given graph to determine whether source is reachable from target.
*
* @param <V>
* the type parameter of the nodes in the graph
* @param source
* the source node
* @param target
* the target node
* @param graph
* the graph data source
* @return true if source is reachable from target, false otherwise
*/
public static <V> boolean isReachable(V source, V target, IGraphDataSource<V> graph) {
Deque<V> nodeQueue = new ArrayDeque<V>();
Set<V> visited = new HashSet<V>();
nodeQueue.add(source);
visited.add(source);
boolean ret = _isReachable(target, graph, nodeQueue, visited);
return ret;
}
private static <V> boolean _isReachable(V target, IGraphDataSource<V> graph, Deque<V> nodeQueue, Set<V> visited) {
while (!nodeQueue.isEmpty()) {
V node = nodeQueue.removeFirst();
for (V t : graph.getTargetNodes(node).distinctValues()){
if (t.equals(target)) {
return true;
}
if (!visited.contains(t)) {
visited.add(t);
nodeQueue.addLast(t);
}
}
}
return false;
}
public static <V> Set<V> reachableSources(IBiDirectionalGraphDataSource<V> graph, V target) {
Set<V> retSet = new HashSet<V>();
retSet.add(target);
Deque<V> nodeQueue = new ArrayDeque<V>();
nodeQueue.add(target);
_reachableSources(graph, nodeQueue, retSet);
return retSet;
}
private static <V> void _reachableSources(IBiDirectionalGraphDataSource<V> graph, Deque<V> nodeQueue,
Set<V> retSet) {
while (!nodeQueue.isEmpty()) {
V node = nodeQueue.removeFirst();
for (V _node : graph.getSourceNodes(node).distinctValues()) {
if (!retSet.contains(_node)) {
retSet.add(_node);
nodeQueue.addLast(_node);
}
}
}
}
public static <V> Set<V> reachableTargets(IGraphDataSource<V> graph, V source) {
Set<V> retSet = new HashSet<V>();
retSet.add(source);
Deque<V> nodeQueue = new ArrayDeque<V>();
nodeQueue.add(source);
_reachableTargets(graph, nodeQueue, retSet);
return retSet;
}
private static <V> void _reachableTargets(IGraphDataSource<V> graph, Deque<V> nodeQueue, Set<V> retSet) {
while (!nodeQueue.isEmpty()) {
V node = nodeQueue.removeFirst();
for (V _node : graph.getTargetNodes(node).distinctValues()) {
if (!retSet.contains(_node)) {
retSet.add(_node);
nodeQueue.addLast(_node);
}
}
}
}
/**
* Performs a breadth first search on the given graph and collects all the nodes along the path from source to
* target if such path exists.
*
* @param <V>
* the type parameter of the nodes in the graph
* @param source
* the source node
* @param target
* the target node
* @param graph
* the graph data source
* @return the set of nodes along the path
*/
public static <V> Set<V> collectNodesAlongPath(V source, V target, IGraphDataSource<V> graph) {
Set<V> path = new HashSet<V>();
_collectNodesAlongPath(source, target, graph, path);
return path;
}
private static <V> boolean _collectNodesAlongPath(V node, V target, IGraphDataSource<V> graph, Set<V> path) {
boolean res = false;
// end recursion
if (node.equals(target)) {
path.add(node);
return true;
} else {
for (V _nodeT : graph.getTargetNodes(node).distinctValues()) {
res = (_collectNodesAlongPath(_nodeT, target, graph, path)) || res;
}
if (res)
path.add(node);
return res;
}
}
}
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