Sudoku_Solver

import java.util.*;
public class Main {
    public static void main(String args[]) {
        // Your Code Here
        int N = scn.nextInt();
        int[][] arr = new int[N][N];
        for (int i = 0; i < arr.length; i++) {
            for (int j = 0; j < arr[0].length; j++) {
                arr[i][j] = scn.nextInt();
            }
        }
         sudoku(arr,0,0);
    }
    static Scanner scn = new Scanner(System.in);
    public static void sudoku(int[][] arr, int row, int col) {
        if (col == arr[0].length) {
            row++;
            col = 0;
        }
        if (row == arr.length) {
            display(arr);
            return;
        }
        if (arr[row][col] != 0) {
            sudoku(arr, row, col + 1);
            return;
        }
        for (int i = 1; i <= 9; i++) {
            if (isItSafe(arr, row, col, i)) {
                arr[row][col] = i;
                sudoku(arr, row, col + 1);
                arr[row][col] = 0;
            }
            
            
        }
    }
    public static boolean isItSafe(int[][] arr, int row, int col, int val) {
        return isitsaferow(arr, row, val) && isitsafecol(arr, col, val) && isitsafecolumn(arr, row, col, val);
    }
    public static boolean isitsaferow(int[][] arr, int row, int i) {
        for (int c = 0; c < arr[0].length; c++) {
            if (arr[row][c] == i) {
                return false;
            }
        }
        return true;
    }
    public static boolean isitsafecol(int[][] arr, int col, int i) {
        for (int r = 0; r < arr.length; r++) {
            if (arr[r][col] == i) {
                return false;
            }
        }
        return true;
    }
    public static boolean isitsafecolumn(int[][] arr, int row, int col, int i) {
        int bsr = row - row % 3;
        int bsc = col - col % 3;
        for (int r = bsr; r < bsr + 3; r++) {
            for (int c = bsc; c < bsc + 3; c++) {
                if (arr[r][c] == i) {
                    return false;
                }
            }
        }
        return true;
    }
    public static void display(int[][] arr) {
        for (int i = 0; i < arr.length; i++) {
            for (int j = 0; j < arr[0].length; j++) {
                System.out.print(arr[i][j] + " ");
            }
            System.out.println();
        }
    }
}