olympic.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 Olympic
{

   public static void minus(Solver solver, 
                            IntVar x, 
                            IntVar y, 
                            IntVar z) 
  {
    solver.Add(z == (x - y).Abs());
  }



  /**
   *
   * Olympic puzzle.
   * 
   * Benchmark for Prolog (BProlog)
   * """
   * File   : olympic.pl
   * Author : Neng-Fa ZHOU
   * Date   : 1993
   *
   * Purpose: solve a puzzle taken from Olympic Arithmetic Contest
   *
   * Given ten variables with the following configuration:
   *
   *                 X7   X8   X9   X10
   *
   *                    X4   X5   X6
   *
   *                       X2   X3
   *
   *                          X1
   *
   * We already know that X1 is equal to 3 and want to assign each variable
   * with a different integer from {1,2,...,10} such that for any three
   * variables
   *                        Xi   Xj
   *
   *                           Xk
   *
   * the following constraint is satisfied:
   *
   *                      |Xi-Xj| = Xk
   * """
   *
   * Also see http://www.hakank.org/or-tools/olympic.py
   *
   */
  private static void Solve()
  {
    Solver solver = new Solver("Olympic");

    //
    // Data
    //
    int n = 10;

    //
    // Decision variables
    //
    IntVar[] x = solver.MakeIntVarArray(n, 1, n, "x");
    IntVar X1  = x[0];
    IntVar X2  = x[1];
    IntVar X3  = x[2];
    IntVar X4  = x[3];
    IntVar X5  = x[4];
    IntVar X6  = x[5];
    IntVar X7  = x[6];
    IntVar X8  = x[7];
    IntVar X9  = x[8];
    IntVar X10 = x[9];


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

    solver.Add(X1 == 3);
    minus(solver, X2, X3, X1);
    minus(solver, X4, X5, X2);
    minus(solver, X5, X6, X3);
    minus(solver, X7, X8, X4);
    minus(solver, X8, X9, X5);
    minus(solver, X9, X10, X6);


    //
    // Search
    //
    DecisionBuilder db = solver.MakePhase(x,
                                          Solver.INT_VAR_SIMPLE,
                                          Solver.INT_VALUE_DEFAULT);

    solver.NewSearch(db);

    while (solver.NextSolution()) {
      for(int i = 0; i < n; i++) {
        Console.Write("{0,2} ", x[i].Value());
      }
      Console.WriteLine();
    }

    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();
  }
}