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/*
 * (C) Copyright 2019-2023, by Dimitrios Michail 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.alg.interfaces;

import java.io.*;
import java.util.*;

/**
 * An algorithm which computes a graph vertex clustering.
 *
 * @param  the graph vertex type
 */
public interface ClusteringAlgorithm
{

    /**
     * Computes a clustering.
     *
     * @return a clustering
     */
    Clustering getClustering();

    /**
     * A clustering. The clusters are integers starting from $0$.
     *
     * @param  the graph vertex type
     */
    interface Clustering
        extends Iterable>
    {
        /**
         * Get the number of clusters.
         * 
         * @return the number of clusters
         */
        int getNumberClusters();

        /**
         * Get the clusters.
         *
         * @return a list of clusters
         */
        List> getClusters();
    }

    /**
     * Default implementation of the clustering interface.
     *
     * @param  the graph vertex type
     */
    class ClusteringImpl
        implements Clustering, Serializable
    {
        private static final long serialVersionUID = -5718903410443848101L;

        private final List> clusters;

        /**
         * Construct a new clustering.
         *
         * @param clusters clusters
         */
        public ClusteringImpl(List> clusters)
        {
            this.clusters = clusters;
        }

        @Override
        public int getNumberClusters()
        {
            return clusters.size();
        }

        @Override
        public List> getClusters()
        {
            return clusters;
        }

        @Override
        public String toString()
        {
            return "Clustering [k=" + clusters.size() + ", clusters=" + clusters + "]";
        }

        @Override
        public Iterator> iterator()
        {
            return clusters.iterator();
        }
    }

}