marathon2.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 Marathon2
{
  /**
   *
   * Marathon puzzle.
   *
   * From Xpress example
   * http://www.dashoptimization.com/home/cgi-bin/example.pl?id=mosel_puzzle_5_3
   * """
   * Dominique, Ignace, Naren, Olivier, Philippe, and Pascal
   * have arrived as the first six at the Paris marathon.
   * Reconstruct their arrival order from the following
   * information:
   * a) Olivier has not arrived last
   * b) Dominique, Pascal and Ignace have arrived before Naren
   *    and Olivier
   * c) Dominique who was third last year has improved this year.
   * d) Philippe is among the first four.
   * e) Ignace has arrived neither in second nor third position.
   * f) Pascal has beaten Naren by three positions.
   * g) Neither Ignace nor Dominique are on the fourth position.
   *
   * (c) 2002 Dash Associates
   * author: S. Heipcke, Mar. 2002
   * """
   *
   * Also see http://www.hakank.org/or-tools/marathon2.py
   *
   */
  private static void Solve()
  {
    Solver solver = new Solver("Marathon2");

    //
    // Data
    //
    int n = 6;
    String[] runners_str = {"Dominique", "Ignace", "Naren",
                            "Olivier", "Philippe", "Pascal"};


    //
    // Decision variables
    //
    IntVar[] runners = solver.MakeIntVarArray(n, 1, n, "runners");
    IntVar Dominique = runners[0];
    IntVar Ignace    = runners[1];
    IntVar Naren     = runners[2];
    IntVar Olivier   = runners[3];
    IntVar Philippe  = runners[4];
    IntVar Pascal    = runners[5];

    //
    // Constraints
    //
    solver.Add(runners.AllDifferent());

    // a: Olivier not last
    solver.Add(Olivier != n);

    // b: Dominique, Pascal and Ignace before Naren and Olivier
    solver.Add(Dominique  < Naren);
    solver.Add(Dominique  < Olivier);
    solver.Add(Pascal     < Naren);
    solver.Add(Pascal     < Olivier);
    solver.Add(Ignace     < Naren);
    solver.Add(Ignace     < Olivier);

    // c: Dominique better than third
    solver.Add(Dominique  < 3);

    // d: Philippe is among the first four
    solver.Add(Philippe   <= 4);

    // e: Ignace neither second nor third
    solver.Add(Ignace     != 2);
    solver.Add(Ignace     != 3);

    // f: Pascal three places earlier than Naren
    solver.Add(Pascal + 3 == Naren);

    // g: Neither Ignace nor Dominique on fourth position
    solver.Add(Ignace     != 4);
    solver.Add(Dominique  != 4);


    //
    // Search
    //
    DecisionBuilder db = solver.MakePhase(runners,
                                          Solver.CHOOSE_MIN_SIZE_LOWEST_MIN,
                                          Solver.ASSIGN_CENTER_VALUE);

    solver.NewSearch(db);

    while (solver.NextSolution()) {
      int[] runners_val = new int[n];      
      Console.Write("runners: ");
      for(int i = 0; i < n; i++) {
        runners_val[i] = (int)runners[i].Value();
        Console.Write(runners_val[i] + " ");
      }
      Console.WriteLine("\nPlaces:");
      for(int i = 1; i < n+1; i++) {
        for(int j = 0; j < n; j++) {
          if (runners_val[j] == i) {
            Console.WriteLine("{0}: {1}", i, runners_str[j]);
          }
        }
      }
    }

    Console.WriteLine("\nSolutions: " + solver.Solutions());
    Console.WriteLine("WallTime: " + solver.WallTime() + "ms ");
    Console.WriteLine("Failures: " + solver.Failures());
    Console.WriteLine("Branches: " + solver.Branches());

    solver.EndSearch();

  }

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