SolutionCreator.java

//SolutionCreator.java
//Description: Was made to create a random 9x9 Sudoku solution
import java.util.Random;
import java.util.Date;
public class SolutionCreator{
    public int [][]solution;
    private Random rand;
    //Constructor
    public SolutionCreator(){
        rand = new Random();
        solution = new int [9][9];
    }
    //Generates a new solution and writes it to public int solution
    public void GenerateSolution(){
        //choose a random simple generic solution of following choices:
        Date d = new Date();
        rand.setSeed(d.getTime());
        switch (rand.nextInt(6)) {
            case 0: int [][] s0 = {{1,2,3,4,5,6,7,8,9},
                                   {4,7,9,1,2,8,6,5,3},
                                   {8,6,5,7,9,3,2,4,1},
                                   {3,9,4,6,7,1,5,2,8},
                                   {5,1,2,9,8,4,3,6,7},
                                   {7,8,6,5,3,2,9,1,4},
                                   {2,4,7,3,1,5,8,9,6},
                                   {6,3,8,2,4,9,1,7,5},
                                   {9,5,1,8,6,7,4,3,2}};
                    solution = s0;
                    break;
            case 1:int [][] s1 = {{1,2,3,4,5,6,7,8,9},
                                  {4,5,9,8,7,1,2,3,6},
                                  {8,7,6,2,3,9,1,4,5},
                                  {3,9,4,6,1,2,5,7,8},
                                  {5,8,2,7,9,3,6,1,4},
                                  {6,1,7,5,4,8,3,9,2},
                                  {2,3,1,9,6,4,8,5,7},
                                  {7,4,8,1,2,5,9,6,3},
                                  {9,6,5,3,8,7,4,2,1}};
                    solution = s1;
                    break;
            case 2:int [][] s2 = {{1,2,3,4,5,6,7,8,9},
                                  {7,8,6,2,9,3,5,1,4},
                                  {9,5,4,7,8,1,6,2,3},
                                  {2,3,1,5,4,9,8,6,7},
                                  {4,6,8,1,7,2,3,9,5},
                                  {5,7,9,6,3,8,1,4,2},
                                  {3,1,2,9,6,5,4,7,8},
                                  {6,4,5,8,2,7,9,3,1},
                                  {8,9,7,3,1,4,2,5,6}};
                    solution = s2;
                    break;
            case 3:int [][] s3 = {{1,2,3,4,5,6,7,8,9},
                                  {7,4,6,9,2,8,1,3,5},
                                  {9,8,5,1,3,7,4,6,2},
                                  {4,3,1,8,7,2,9,5,6},
                                  {6,7,9,5,1,3,2,4,8},
                                  {8,5,2,6,4,9,3,7,1},
                                  {2,9,8,7,6,4,5,1,3},
                                  {3,1,4,2,8,5,6,9,7},
                                  {5,6,7,3,9,1,8,2,4}};
                    solution = s3;
                    break;
            case 4:int [][] s4 = {{1,2,3,4,5,6,7,8,9},
                                  {4,7,8,2,9,1,6,5,3},
                                  {6,9,5,3,7,8,4,1,2},
                                  {3,1,2,7,6,4,8,9,5},
                                  {8,5,6,1,3,9,2,4,7},
                                  {9,4,7,8,2,5,3,6,1},
                                  {2,6,9,5,4,7,1,3,8},
                                  {5,3,1,6,8,2,9,7,4},
                                  {7,8,4,9,1,3,5,2,6}};
                    solution = s4;
                    break;
            default:int [][] s5 = {{1,2,3,4,5,6,7,8,9},
                                   {6,7,8,3,2,9,5,1,4},
                                   {9,4,5,8,1,7,2,6,3},
                                   {2,1,6,9,4,5,8,3,7},
                                   {3,9,7,6,8,2,1,4,5},
                                   {5,8,4,7,3,1,6,9,2},
                                   {4,6,2,5,9,8,3,7,1},
                                   {7,5,9,1,6,3,4,2,8},
                                   {8,3,1,2,7,4,9,5,6}};
                    solution = s5;
                    break;
        }
        //randomize solution
        for(int i=0;i<rand.nextInt(51)+50;i++){
            //swap numbers
            int num1 = rand.nextInt(9)+1;
            int num2 = rand.nextInt(9)+1;
            while(num1==num2)num2 = rand.nextInt(9)+1;
            for(int r=0;r<9;r++){
                for(int c=0;c<9;c++){
                    if(solution[r][c]==num1)solution[r][c]=num2;
                    else if(solution[r][c]==num2)solution[r][c]=num1;
                }
            }
            //column swapper
            for(int c=0;c<3;c++){
                int c1 = rand.nextInt(3);
                int c2 = rand.nextInt(3);
                while(c1==c2)c2 = rand.nextInt(3);
                for(int r=0;r<9;r++){
                    int tmp = solution[r][c1+c*3];
                    solution[r][c1+c*3]=solution[r][c2+c*3];
                    solution[r][c2+c*3]=tmp;
                }
            }
            //row swapper
            for(int r=0;r<3;r++){
                if(rand.nextFloat()<.5){
                    int r1 = rand.nextInt(3);
                    int r2 = rand.nextInt(3);
                    while(r1==r2)r2 = rand.nextInt(3);
                    for(int c=0;c<9;c++){
                        int tmp = solution[r1+r*3][c];
                        solution[r1+r*3][c]=solution[r2+r*3][c];
                        solution[r2+r*3][c]=tmp;
                    }
                }
            }
        }
    }
    //Prints the solution
    public void PrintSolution(){
        for(int r=0;r<9;r++){
            for(int c=0;c<9;c++){
                System.out.print(solution[r][c]);
                if(c==2||c==5)System.out.print("|");
            }
            System.out.println();
            if(r==2||r==5)System.out.println("---+---+---");
        }
    }
}