124 lines
3.2 KiB
C#
124 lines
3.2 KiB
C#
//
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// Copyright 2012 Hakan Kjellerstrand
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//
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// Licensed under the Apache License, Version 2.0 (the "License");
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// you may not use this file except in compliance with the License.
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// You may obtain a copy of the License at
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//
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// http://www.apache.org/licenses/LICENSE-2.0
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//
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// Unless required by applicable law or agreed to in writing, software
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// distributed under the License is distributed on an "AS IS" BASIS,
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// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
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// See the License for the specific language governing permissions and
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// limitations under the License.
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using System;
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using System.Linq;
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using Google.OrTools.ConstraintSolver;
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public class NQueens
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{
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/**
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*
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* Solves the N-Queens problem.
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*
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* Syntax: nqueens.exe n num print
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* where
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* n : size of board
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* num : number of solutions to calculate
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* print: print the results (if > 0)
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*
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*/
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private static void Solve(int n = 8, int num = 0, int print = 1)
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{
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Solver solver = new Solver("N-Queens");
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//
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// Decision variables
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//
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IntVar[] q = solver.MakeIntVarArray(n, 0, n - 1, "q");
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//
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// Constraints
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//
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solver.Add(q.AllDifferent());
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IntVar[] q1 = new IntVar[n];
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IntVar[] q2 = new IntVar[n];
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for (int i = 0; i < n; i++)
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{
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q1[i] = (q[i] + i).Var();
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q2[i] = (q[i] - i).Var();
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}
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solver.Add(q1.AllDifferent());
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solver.Add(q2.AllDifferent());
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// Alternative version: it works as well but are not that clear
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/*
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solver.Add((from i in Enumerable.Range(0, n)
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select (q[i] + i).Var()).ToArray().AllDifferent());
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solver.Add((from i in Enumerable.Range(0, n)
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select (q[i] - i).Var()).ToArray().AllDifferent());
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*/
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//
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// Search
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//
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DecisionBuilder db = solver.MakePhase(q, Solver.CHOOSE_MIN_SIZE_LOWEST_MAX, Solver.ASSIGN_CENTER_VALUE);
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solver.NewSearch(db);
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int c = 0;
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while (solver.NextSolution())
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{
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if (print > 0)
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{
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for (int i = 0; i < n; i++)
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{
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Console.Write("{0} ", q[i].Value());
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}
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Console.WriteLine();
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}
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c++;
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if (num > 0 && c >= num)
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{
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break;
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}
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}
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Console.WriteLine("\nSolutions: {0}", solver.Solutions());
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Console.WriteLine("WallTime: {0}ms", solver.WallTime());
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Console.WriteLine("Failures: {0}", solver.Failures());
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Console.WriteLine("Branches: {0} ", solver.Branches());
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solver.EndSearch();
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}
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public static void Main(String[] args)
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{
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int n = 8;
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int num = 0;
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int print = 1;
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if (args.Length > 1)
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{
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n = Convert.ToInt32(args[1]);
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}
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if (args.Length > 2)
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{
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num = Convert.ToInt32(args[2]);
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}
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if (args.Length > 3)
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{
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print = Convert.ToInt32(args[3]);
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}
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Console.WriteLine("n: {0} num: {1} print: {2}", n, num, print);
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Solve(n, num, print);
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}
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}
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