valid sudoku leetcode

class Solution {
    public boolean isValidSudoku(char[][] board) {
        byte[][] c = new byte[9][10];
        byte[] r = null;
        byte[][] b = null;
        for(int i = 0; i < 9; i++ ){
            
            r = new byte[10];        
            
            for(int j = 0; j < 9; j++){
                if(i % 3 == 0 && j == 0){
                    b = new byte[3][10];                    
                }
                if(board[i][j] == '.'){
                    continue;
                }
                byte t = (byte)(board[i][j] - 48);
                if(c[j][t] == t
                  || r[t] == t
                  || b[j/3][t] == t){
                    return false;
                }
                c[j][t] = b[j/3][t] = r[t] = t;
                
            }
        }
        
        return true;
    }
}