net.automatalib.util.graphs.traversal.DepthFirstIterator Maven / Gradle / Ivy
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This artifact provides various common utility operations for analyzing and manipulating
automata and graphs, such as traversal, minimization and copying.
/* Copyright (C) 2013-2014 TU Dortmund
* This file is part of AutomataLib, http://www.automatalib.net/.
*
* AutomataLib is free software; you can redistribute it and/or
* modify it under the terms of the GNU Lesser General Public
* License version 3.0 as published by the Free Software Foundation.
*
* AutomataLib is distributed in the hope that it will be useful,
* but WITHOUT ANY WARRANTY; without even the implied warranty of
* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
* Lesser General Public License for more details.
*
* You should have received a copy of the GNU Lesser General Public
* License along with AutomataLib; if not, see
* http://www.gnu.de/documents/lgpl.en.html.
*/
package net.automatalib.util.graphs.traversal;
import java.util.ArrayDeque;
import java.util.Collection;
import java.util.Deque;
import net.automatalib.commons.util.mappings.MutableMapping;
import net.automatalib.graphs.IndefiniteGraph;
import net.automatalib.util.traversal.VisitedState;
import com.google.common.collect.AbstractIterator;
final class DepthFirstIterator extends AbstractIterator {
private final MutableMapping visited;
private final Deque> dfsStack
= new ArrayDeque<>();
private final IndefiniteGraph graph;
public DepthFirstIterator(IndefiniteGraph graph, Collection start) {
this.graph = graph;
this.visited = graph.createStaticNodeMapping();
for(N startNode : start) {
dfsStack.push(new SimpleDFRecord(startNode));
}
}
@Override
protected N computeNext() {
SimpleDFRecord rec;
while((rec = dfsStack.peek()) != null) {
if(!rec.wasStarted()) {
visited.put(rec.node, VisitedState.VISITED);
rec.start(graph);
return rec.node;
}
else if(rec.hasNextEdge()) {
E edge = rec.nextEdge();
N tgt = graph.getTarget(edge);
if(visited.get(tgt) != VisitedState.VISITED) {
dfsStack.push(new SimpleDFRecord(tgt));
}
}
else {
dfsStack.pop();
}
}
return endOfData();
}
}