// Copyright 2011 Hakan Kjellerstrand hakank@gmail.com // Licensed under the Apache License, Version 2.0 (the "License"); // you may not use this file except in compliance with the License. // You may obtain a copy of the License at // // http://www.apache.org/licenses/LICENSE-2.0 // // Unless required by applicable law or agreed to in writing, software // distributed under the License is distributed on an "AS IS" BASIS, // WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. // See the License for the specific language governing permissions and // limitations under the License. package com.google.ortools.examples; import com.google.ortools.constraintsolver.DecisionBuilder; import com.google.ortools.constraintsolver.IntVar; import com.google.ortools.constraintsolver.Solver; import java.io.*; import java.text.*; import java.util.*; public class NQueens2 { static { System.loadLibrary("jniortools"); } /** Solves the N Queens problem. See http://www.hakank.org/google_or_tools/nqueens2.py */ private static void solve(int n, int num, int print) { Solver solver = new Solver("NQueens"); System.out.println("n: " + n); // // variables // IntVar[] q = solver.makeIntVarArray(n, 0, n - 1, "q"); // // constraints // solver.addConstraint(solver.makeAllDifferent(q)); IntVar[] q1 = new IntVar[n]; IntVar[] q2 = new IntVar[n]; for (int i = 0; i < n; i++) { q1[i] = solver.makeSum(q[i], i).var(); q2[i] = solver.makeSum(q[i], -i).var(); } solver.addConstraint(solver.makeAllDifferent(q1)); solver.addConstraint(solver.makeAllDifferent(q2)); // // Solve // DecisionBuilder db = solver.makePhase(q, solver.CHOOSE_MIN_SIZE_LOWEST_MAX, solver.ASSIGN_CENTER_VALUE); solver.newSearch(db); int c = 0; while (solver.nextSolution()) { if (print != 0) { for (int i = 0; i < n; i++) { System.out.print(q[i].value() + " "); } System.out.println(); } c++; if (num > 0 && c >= num) { break; } } solver.endSearch(); // Statistics System.out.println(); System.out.println("Solutions: " + solver.solutions()); System.out.println("Failures: " + solver.failures()); System.out.println("Branches: " + solver.branches()); System.out.println("Wall time: " + solver.wallTime() + "ms"); } public static void main(String[] args) throws Exception { int n = 8; int num = 0; int print = 1; if (args.length > 0) { n = Integer.parseInt(args[0]); } if (args.length > 1) { num = Integer.parseInt(args[1]); } if (args.length > 2) { print = Integer.parseInt(args[2]); } NQueens2.solve(n, num, print); } }