org.xcsp.modeler.problems.Queens Maven / Gradle / Ivy

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Java Tools for parsing XCSP3 instances, compiling JvCSP3 models, and checking solutions. For more information about XCSP3, follow www.xcsp.org

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/**
 * AbsCon - Copyright (c) 2017, CRIL-CNRS - [email protected]
 * 
 * All rights reserved.
 * 
 * This program and the accompanying materials are made available under the terms of the CONTRAT DE LICENCE DE LOGICIEL LIBRE CeCILL which accompanies this
 * distribution, and is available at http://www.cecill.info
 */
package org.xcsp.modeler.problems;

import org.xcsp.common.IVar.Var;
import org.xcsp.modeler.api.ProblemAPI;

public class Queens implements ProblemAPI {
	int n; // number of queens

	@Override
	public void model() {
		Var[] q = array("q", size(n), dom(range(n)), "q[i] is the column where is put the ith queen (at row i)");

		if (modelVariant("m1")) {
			forall(range(n).range(n), (i, j) -> {
				if (i < j)
					conjunction(ne(q[i], q[j]), ne(dist(q[i], q[j]), dist(i, j)));
			});
		}
		if (modelVariant("m2")) {
			allDifferent(q);
			forall(range(n).range(n), (i, j) -> {
				if (i < j)
					different(dist(q[i], q[j]), dist(i, j));
			});
		}
		if (modelVariant("m3")) {
			allDifferent(q);
			allDifferent(treesFrom(range(n), i -> add(q[i], i)));
			allDifferent(treesFrom(range(n), i -> sub(q[i], i)));
		}
	}
}