sudoku.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.Collections.Generic;
using System.Linq;
using System.Text.RegularExpressions;
using Google.OrTools.ConstraintSolver;


public class Sudoku
{

  /**
   *
   * Solves a Sudoku problem.
   *
   */
  private static void Solve()
  {
    Solver solver = new Solver("Sudoku");

    //
    // data
    //
    int cell_size = 3;
    IEnumerable<int> CELL = Enumerable.Range(0, cell_size);
    int n = cell_size * cell_size;
    IEnumerable<int> RANGE = Enumerable.Range(0, n);

    // 0 marks an unknown value
    int[,] initial_grid = {{0, 6, 0, 0, 5, 0, 0, 2, 0},
                           {0, 0, 0, 3, 0, 0, 0, 9, 0},
                           {7, 0, 0, 6, 0, 0, 0, 1, 0},
                           {0, 0, 6, 0, 3, 0, 4, 0, 0},
                           {0, 0, 4, 0, 7, 0, 1, 0, 0},
                           {0, 0, 5, 0, 9, 0, 8, 0, 0},
                           {0, 4, 0, 0, 0, 1, 0, 0, 6},
                           {0, 3, 0, 0, 0, 8, 0, 0, 0},
                           {0, 2, 0, 0, 4, 0, 0, 5, 0}};


    //
    // Decision variables
    //
    IntVar[,] grid =  solver.MakeIntVarMatrix(n, n, 1, 9, "grid");
    IntVar[] grid_flat = grid.Flatten();

    //
    // Constraints
    //

    // init
    foreach(int i in RANGE) {
      foreach(int j in RANGE) {
        if (initial_grid[i,j] > 0) {
          solver.Add(grid[i,j] == initial_grid[i,j]);
        }
      }
    }


    foreach(int i in RANGE) {

      // rows
      solver.Add( (from j in RANGE
                   select grid[i,j]).ToArray().AllDifferent());

      // cols
      solver.Add( (from j in RANGE
                   select grid[j,i]).ToArray().AllDifferent());

    }

    // cells
    foreach(int i in CELL) {
      foreach(int j in CELL) {
        solver.Add( (from di in CELL
                     from dj in CELL
                     select grid[i*cell_size+di, j*cell_size+dj]
                     ).ToArray().AllDifferent());
      }
    }


    //
    // Search
    //
    DecisionBuilder db = solver.MakePhase(grid_flat,
                                          Solver.INT_VAR_SIMPLE,
                                          Solver.INT_VALUE_SIMPLE);

    solver.NewSearch(db);

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

      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();
  }
}