com.almondtools.util.graph.ReversePostOrderWorklistTraversal Maven / Gradle / Ivy

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Regular expression matchers, searcher, lexers based on deterministic finite automata

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package com.almondtools.util.graph;

import java.util.HashSet;
import java.util.Iterator;
import java.util.LinkedHashSet;
import java.util.LinkedList;
import java.util.List;
import java.util.Set;

public abstract class ReversePostOrderWorklistTraversal extends AbstractTraversal implements Traversal {

	private Class clazz;
	private Set> visited;
	private List> ordered;
	private Set> worklist;

	public ReversePostOrderWorklistTraversal(Graph graph, Class clazz) {
		super(graph);
		this.clazz = clazz;
		this.visited = new HashSet>();
		this.ordered = new LinkedList>();
	}

	@Override
	public void traverse() {
		super.traverse();
		this.worklist = new LinkedHashSet>();
		worklist.addAll(getGraph().getNodes());
		while (!worklist.isEmpty()) {
			if (worklist.size() == 1) {
				Iterator> iterator = worklist.iterator();
				GraphNode node = iterator.next();
				iterator.remove();
				visitGraphNodeWorklist(node);
			} else {
				for (GraphNode node : ordered) {
					if (worklist.contains(node)) {
						worklist.remove(node);
						visitGraphNodeWorklist(node);
					}
				}
			}
		}
	}

	private void visitGraphNodeWorklist(GraphNode node) {
		V oldData = getData(node, clazz);
		visitGraphNode(node);
		V newData = getData(node, clazz);
		if (oldData == newData) {
			return;
		} else if (oldData == null) {
			worklist.addAll(node.getSuccessors());
		} else if (newData == null) {
			worklist.addAll(node.getSuccessors());
		} else if (oldData.equals(newData)) {
			return;
		} else {
			worklist.addAll(node.getSuccessors());
		}
	}

	@Override
	public void traverseNode(GraphNode node) {
		if (!visited.contains(node)) {
			visited.add(node);
			for (GraphNode next : node.getSuccessors()) {
				next.apply(this);
			}
			record(node);
		}
	}

	private void record(GraphNode node) {
		ordered.add(0, node);
	}

	public abstract void visitGraphNode(GraphNode node);

}