Problem: Valid Sudoku

Determine if a 9 x 9 Sudoku board is valid. Only the filled cells need to be validated according to the following rules:

//Each row must contain the digits 1-9 without repetition. //Each column must contain the digits 1-9 without repetition. //Each of the nine 3 x 3 sub-boxes of the grid must contain the digits 1-9 without repetition.

Note:

A Sudoku board (partially filled) could be valid but is not necessarily solvable. Only the filled cells need to be validated according to the mentioned rules.

class Solution {
    public boolean isValid(char[][] board, int row,int col,char val){
        for(int i=0;i<9;i++){
            if(board[row][i] == val) return false;
            if(board[i][col] == val) return false;
            if(board[3*(row/3)+i/3][3*(col/3)+i%3] == val) return false;
        }
        return true;
    }
    public boolean isValidSudoku(char[][] board) {
        boolean res = true;
        for(int i=0;i<9;i++){
            for(int j=0;j<9;j++){
                if(board[i][j] != '.'){
                    if(board[i][j] != '.'){
                    char val = board[i][j];
                    board[i][j] = '.';
                    res = isValid(board,i,j,val);
                    board[i][j] = val;
                    }
                   if(!res) return res; 
                }
            }
        }
        return true;
    }
}