Sudoku Solver

public class Solution {    public boolean isValid(char[][] board, int x, int y){int i, j;for(i = 0; i < 9; i++)if(i != x && board[i][y] == board[x][y])return false;for(j = 0; j < 9; j++)if(j != y && board[x][j] == board[x][y])return false;for(i = 3 * (x / 3); i < 3 * (x / 3 + 1); i++)for(j = 3 * (y / 3); j < 3 * (y / 3 + 1); j++)if(i != x && j != y && board[i][j] == board[x][y])return false;return true;}public boolean solveSudokuDFS(char[][] board) {for(int i = 0; i < 9; i++){for(int j = 0; j < 9; j++){if(board[i][j] == '.'){for(int k = 1; k <= 9; k++){board[i][j] = (char)('0' + k);if(isValid(board, i, j) && solveSudokuDFS(board))return true;board[i][j] = '.';}return false;}}}return true;}public void solveSudoku(char[][] board) {// Start typing your Java solution below// DO NOT write main() functionsolveSudokuDFS(board);}}