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A graph module for Choco Solver.
There is a newer version: 4.2.2
/*
 * Copyright (c) 1999-2014, Ecole des Mines de Nantes
 * All rights reserved.
 * Redistribution and use in source and binary forms, with or without
 * modification, are permitted provided that the following conditions are met:
 *
 *     * Redistributions of source code must retain the above copyright
 *       notice, this list of conditions and the following disclaimer.
 *     * Redistributions in binary form must reproduce the above copyright
 *       notice, this list of conditions and the following disclaimer in the
 *       documentation and/or other materials provided with the distribution.
 *     * Neither the name of the Ecole des Mines de Nantes nor the
 *       names of its contributors may be used to endorse or promote products
 *       derived from this software without specific prior written permission.
 *
 * THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND ANY
 * EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED
 * WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE
 * DISCLAIMED. IN NO EVENT SHALL THE REGENTS AND CONTRIBUTORS BE LIABLE FOR ANY
 * DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES
 * (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES;
 * LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND
 * ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
 * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF THIS
 * SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
 */
package org.chocosolver.graphsolver.search.strategy.arcs;

import gnu.trove.list.array.TIntArrayList;
import org.chocosolver.graphsolver.search.strategy.ArcStrategy;
import org.chocosolver.graphsolver.variables.IGraphVar;
import org.chocosolver.util.objects.setDataStructures.ISet;

import java.util.Random;

public class RandomArc extends ArcStrategy {

    private Random rd;
    private TIntArrayList pFrom, pTo;

    public RandomArc(IGraphVar g, long seed) {
        super(g);
        rd = new Random(seed);
        pFrom = new TIntArrayList();
        pTo = new TIntArrayList();
    }

    @Override
    public boolean computeNextArc() {
        pFrom.clear();
        pTo.clear();
        ISet envSuc, kerSuc;
        for (int i : envNodes) {
            envSuc = g.getPotSuccOrNeighOf(i);
            kerSuc = g.getMandSuccOrNeighOf(i);
            if (envSuc.size() != kerSuc.size()) {
                for (int j : envSuc) {
                    if (!kerSuc.contains(j)) {
                        pFrom.add(i);
                        pTo.add(j);
                    }
                }
            }
        }
        if (pFrom.isEmpty()) {
            this.from = this.to = -1;
            return false;
        } else {
            int idx = rd.nextInt(pFrom.size());
            this.from = pFrom.get(idx);
            this.to = pTo.get(idx);
            return true;
        }
    }
}