JavaCodes/sudoku.java at main · MayankRai89/JavaCodes · GitHub

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public class sudoku{
    public static boolean issafe(int sudoku [][], int row, int col, int digit){
        //column
        for(int i = 0; i <= 8; i++){
            if(sudoku[i][col] == digit){
                return false;
            }
        }
        // row
        for(int j = 0; j<=8; j++){
            if(sudoku[row][j]== digit){
                return false;
            }
        }
        // grid
        int sr = (row/3)*3;
        int sc = (col/3)*3;
        for(int i = sr; i<sr+3; i++){
            for(int j = sc; j< sc+3; j++){
                if(sudoku[i][j]==digit){
                    return false;
                }
            }
        }
        return true;
    }
    public static boolean sudokuSolver(int sudoku[][], int row, int col){
        // base case
        if(row == 9 && col == 0){
            return true;
        }

        // recursion
        int nextrow= row, nextcol= col+1;
        if(col+1 == 9)
        {
            nextrow=row+1;
            nextcol=0;
        }
        if(sudoku[row][col] != 0){
            return sudokuSolver(sudoku, nextrow, nextcol);
        }
        for(int digit=1; digit<=9; digit++)
        {
            if(issafe(sudoku, row, col, digit)){
                sudoku[row][col]= digit;
                if(sudokuSolver(sudoku, nextrow, nextcol)){
                    return true;
                }
                sudoku[row][col] = 0;
            }
        }
        return false;
    }
    public static void printSudoku(int sudoku[][]){
        for(int i  = 0; i<9;i++){
            for(int j = 0; j<9; j++){
                System.out.print(sudoku[i][j]+" ");
            }
            System.out.println();
        }
    }
    public static void main(String args[])
    {
        int sudoku[][]={{0, 0, 8, 0, 0, 0, 0, 0, 0},
        {4, 9, 0, 1, 5, 7, 0, 0, 2},
        {0, 0, 3, 0, 0, 4, 1, 9, 0},
        {1, 8, 5, 0, 6, 0, 0, 2, 0},
        {0, 0, 0, 0, 2, 0, 0, 6, 0},
        {9, 6, 0, 4, 0, 5, 3, 0, 0},
        {0, 3, 0, 0, 7, 2, 0, 0, 4},
        {0, 4, 9, 0, 3, 0, 0, 5, 7},
        {8, 2, 7, 0, 0, 9, 0, 1, 3}};
        if(sudokuSolver(sudoku, 0,0))
        {
            System.out.println("solution exists");
           printSudoku(sudoku);
        }
        else
        {
            System.out.println("Solution doesn't exist");
        }
    }
}