circuit2.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 System.Collections;
using System.IO;
using System.Text.RegularExpressions;
using Google.OrTools.ConstraintSolver;


public class CircuitTest2
{


  /**
   * circuit(solver, x, z)
   *
   * A decomposition of the global constraint circuit, based
   * on some observation of the orbits in an array.
   *
   * This version also exposes z (the path) to the public.
   *
   * Note: The domain of x must be 0..n-1 (not 1..n)
   * since C# is 0-based.
   */
  public static void circuit(Solver solver, IntVar[] x, IntVar[] z) {

    int n = x.Length;

    solver.Add(x.AllDifferent());
    solver.Add(z.AllDifferent());

    // put the orbit of x[0] in z[0..n-1]
    solver.Add(z[0] == x[0]);
    for(int i = 1; i < n-1; i++) {
      solver.Add(z[i] == x.Element(z[i-1]));
    }

    // z may not be 0 for i < n-1
    for(int i = 1; i < n - 1; i++) {
      solver.Add(z[i] != 0);
    }

    // when i = n-1 it must be 0
    solver.Add(z[n - 1] == 0);

  }

  /**
   *
   * Implements a (decomposition) of the global constraint circuit
   * and extracting the path.
   *
   * One circuit for n = 5 is    3 0 4 2 1
   * Thus the extracted path is  0 -> 3 -> 2 -> 4 -> 1 -> 0
   *
   */
  private static void Solve(int n = 5)
  {
    Solver solver = new Solver("CircuitTest2");


    //
    // Decision variables
    //
    IntVar[] x = solver.MakeIntVarArray(n, 0, n-1, "x");
    IntVar[] path = solver.MakeIntVarArray(n, 0, n-1, "path");

    //
    // Constraints
    //
    circuit(solver, x, path);



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


    solver.NewSearch(db);

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

    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)
  {
    int n = 5;
    if (args.Length > 0) {
      n = Convert.ToInt32(args[0]);
    }

    Solve(n);
  }
}