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Sudoku.java
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Sudoku.java
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// Copyright 2011 Hakan Kjellerstrand [email protected]
// 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.
package com.google.ortools.contrib;
import com.google.ortools.Loader;
import com.google.ortools.constraintsolver.DecisionBuilder;
import com.google.ortools.constraintsolver.IntVar;
import com.google.ortools.constraintsolver.Solver;
import java.io.*;
import java.text.*;
import java.util.*;
public class Sudoku {
/** Solves a Sudoku problem. */
private static void solve() {
Solver solver = new Solver("Sudoku");
int cell_size = 3;
int n = cell_size * cell_size;
// 0 marks an unknown value
int[][] initial_grid = new int[][] {{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}};
//
// variables
//
IntVar[][] grid = new IntVar[n][n];
IntVar[] grid_flat = new IntVar[n * n];
for (int i = 0; i < n; i++) {
for (int j = 0; j < n; j++) {
grid[i][j] = solver.makeIntVar(1, 9, "grid[" + i + "," + j + "]");
grid_flat[i * n + j] = grid[i][j];
}
}
//
// constraints
//
// init and rows
for (int i = 0; i < n; i++) {
IntVar[] row = new IntVar[n];
for (int j = 0; j < n; j++) {
if (initial_grid[i][j] > 0) {
solver.addConstraint(solver.makeEquality(grid[i][j], initial_grid[i][j]));
}
row[j] = grid[i][j];
}
solver.addConstraint(solver.makeAllDifferent(row));
}
// columns
for (int j = 0; j < n; j++) {
IntVar[] col = new IntVar[n];
for (int i = 0; i < n; i++) {
col[i] = grid[i][j];
}
solver.addConstraint(solver.makeAllDifferent(col));
}
// cells
for (int i = 0; i < cell_size; i++) {
for (int j = 0; j < cell_size; j++) {
IntVar[] cell = new IntVar[n];
for (int di = 0; di < cell_size; di++) {
for (int dj = 0; dj < cell_size; dj++) {
cell[di * cell_size + dj] = grid[i * cell_size + di][j * cell_size + dj];
}
}
solver.addConstraint(solver.makeAllDifferent(cell));
}
}
//
// 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++) {
System.out.print(grid[i][j].value() + " ");
}
System.out.println();
}
System.out.println();
}
solver.endSearch();
// Statistics
System.out.println();
System.out.println("Solutions: " + solver.solutions());
System.out.println("Failures: " + solver.failures());
System.out.println("Branches: " + solver.branches());
System.out.println("Wall time: " + solver.wallTime() + "ms");
}
public static void main(String[] args) throws Exception {
Loader.loadNativeLibraries();
Sudoku.solve();
}
}