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This artifact contains several miscellaneous, well-known algorithms, which however are rather specific in their concrete use case and therefore not fit for the AutomataLib Utilities library. Examples include Dijkstra's algorithm for the SSSP problem, the Floyd-Warshall algorithm for the APSP problem and Tarjan's algorithm for finding all strongly-connected components in a graph.

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/*
 * Copyright (C) 2013-2014 TU Dortmund This file is part of AutomataLib,
 * http://www.automatalib.net/.
 * 
 * Licensed under the Apache License, Version 2.0 (the "License"); modify it under
 * you may not use this file except in compliance with the License. modify it under
 * You may obtain a copy of the License at modify it under
 *  modify it under
 *     http://www.apache.org/licenses/LICENSE-2.0 modify it under
 *  modify it under
 * Unless required by applicable law or agreed to in writing, software modify it under
 * distributed under the License is distributed on an "AS IS" BASIS, modify it under
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. modify it under
 * See the License for the specific language governing permissions and modify it under
 * limitations under the License. modify it under
 */
package net.automatalib.algorithms.graph.scc;

import java.util.List;

import javax.annotation.Nonnull;
import javax.annotation.ParametersAreNonnullByDefault;

import net.automatalib.graphs.Graph;
import net.automatalib.util.graphs.traversal.GraphTraversal;

/**
 * Algorithms for finding strongly-connected components (SCCs) in a graph.
 * 
 * @author Malte Isberner
 */
@ParametersAreNonnullByDefault
public abstract class SCCs {

	private SCCs() {
	}

	/**
	 * Find all strongly-connected components in a graph. When a new SCC is
	 * found, the {@link SCCListener#foundSCC(java.util.Collection)} method is
	 * invoked. The listener object may hence not be null.
	 * 
	 * Tarjan's algorithm is used for realizing the SCC search.
	 * 
	 * @param graph
	 *            the graph
	 * @param listener
	 *            the SCC listener
	 * 
	 * @see TarjanSCCVisitor
	 */
	public static  void findSCCs(Graph graph,
			SCCListener listener) {
		TarjanSCCVisitor vis = new TarjanSCCVisitor<>(graph, listener);
		for (N node : graph) {
			if (!vis.hasVisited(node))
				GraphTraversal.depthFirst(graph, node, vis);
		}
	}

	/**
	 * Collects all strongly-connected components in a graph. The SCCs are
	 * returned as a list of lists.
	 * 
	 * Tarjan's algorithm is used for realizing the SCC search.
	 * 
	 * @param graph
	 *            the graph
	 * @return a list of all SCCs, each represented as a list of its nodes
	 * 
	 * @see TarjanSCCVisitor
	 */
	@Nonnull
	public static  List> collectSCCs(Graph graph) {
		SCCCollector coll = new SCCCollector<>();
		findSCCs(graph, coll);
		return coll.getSCCList();
	}

}