map.cs

//
// Copyright 2012 Hakan Kjellerstrand
//
// 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.

using System;
using Google.OrTools.ConstraintSolver;

public class Map
{
    /**
     *
     * Solves a simple map coloring  problem.
     *
     * See http://www.hakank.org/google_or_tools/map.py
     *
     */
    private static void Solve()
    {
        Solver solver = new Solver("Map");

        //
        // data
        //
        int Belgium = 0;
        int Denmark = 1;
        int France = 2;
        int Germany = 3;
        int Netherlands = 4;
        int Luxembourg = 5;

        int n = 6;
        int max_num_colors = 4;

        //
        // Decision variables
        //
        IntVar[] color = solver.MakeIntVarArray(n, 1, max_num_colors, "color");

        //
        // Constraints
        //
        solver.Add(color[France] != color[Belgium]);
        solver.Add(color[France] != color[Luxembourg]);
        solver.Add(color[France] != color[Germany]);
        solver.Add(color[Luxembourg] != color[Germany]);
        solver.Add(color[Luxembourg] != color[Belgium]);
        solver.Add(color[Belgium] != color[Netherlands]);
        solver.Add(color[Belgium] != color[Germany]);
        solver.Add(color[Germany] != color[Netherlands]);
        solver.Add(color[Germany] != color[Denmark]);

        // Symmetry breaking
        solver.Add(color[Belgium] == 1);

        //
        // Search
        //
        DecisionBuilder db = solver.MakePhase(color, Solver.CHOOSE_MIN_SIZE_LOWEST_MAX, Solver.ASSIGN_CENTER_VALUE);

        solver.NewSearch(db);
        while (solver.NextSolution())
        {
            Console.Write("colors: ");
            for (int i = 0; i < n; i++)
            {
                Console.Write("{0} ", color[i].Value());
            }

            Console.WriteLine();
        }

        Console.WriteLine("\nSolutions: {0}", solver.Solutions());
        Console.WriteLine("WallTime: {0} ms", solver.WallTime());
        Console.WriteLine("Failures: {0}", solver.Failures());
        Console.WriteLine("Branches: {0} ", solver.Branches());

        solver.EndSearch();
    }

    public static void Main(String[] args)
    {
        Solve();
    }
}