Everytime forget to - '0'!!!!!!!

1 class Solution { 2 public: 3     bool isValid(vector
     
       &rec, int value) { 4         if (value < 0) return true; 5         if (rec[value]) return false; 6         rec[value] = true; 7         return true; 8     } 9     bool isValidSudoku(vector
      
       
         > &board) {10         if (board.size() != 9 || board[0].size() != 9) return false;11         for (int i = 0; i < 9; i++) {12             vector
        
          row(10, false), column(10, false), sub(10, false);13             for (int j = 0; j < 9; j++) {14                 if (!isValid(row, board[i][j] - '0') ||15                     !isValid(column, board[j][i] - '0') ||16                     !isValid(sub, board[(i/3)*3 + j/3][(i%3)*3 + j%3] - '0')) {17                         return false;18                 }19             }20         }21         return true;22     }23 };