121 lines
3.4 KiB
Java
121 lines
3.4 KiB
Java
// 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.
|
|
|
|
import java.io.*;
|
|
import java.util.*;
|
|
import java.text.*;
|
|
|
|
import com.google.ortools.constraintsolver.DecisionBuilder;
|
|
import com.google.ortools.constraintsolver.IntVar;
|
|
import com.google.ortools.constraintsolver.Solver;
|
|
|
|
public class NQueens {
|
|
|
|
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 b = solver.makeIntVar(1, 1, "b");
|
|
IntVar[] q1 = new IntVar[n];
|
|
IntVar[] q2 = new IntVar[n];
|
|
for(int i = 0; i < n; i++) {
|
|
for(int j = 0; j < i; j++) {
|
|
// // q[i]+i != q[j]+j
|
|
solver.addConstraint(
|
|
solver.makeNonEquality(
|
|
solver.makeSum(q[i],i).var(),
|
|
solver.makeSum(q[j],j).var()));
|
|
|
|
// q[i]-i != q[j]-j
|
|
solver.addConstraint(
|
|
solver.makeNonEquality(solver.makeSum(q[i],-i).var(),
|
|
solver.makeSum(q[j],-j).var()));
|
|
}
|
|
}
|
|
|
|
//
|
|
// 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]);
|
|
}
|
|
|
|
|
|
NQueens.solve(n, num, print);
|
|
}
|
|
}
|