1
    for(int i=0; i<9; i++){
2
         for(int j=0; j<9; j++){
3
          if(board[i][j] != '.'){ 
4
              char currentVal = board[i][j];
5
               if(!(seen.add(currentVal + "found in row "+ i)) ||
6
                  !(seen.add(currentVal + "found in column "+ j) ) ||
7
                  !(seen.add(currentVal + "found in sub box "+ i/3 + "-"+ j/3)))
8
                   return false;
9
          }
10

11
       } 
12

13
    }
14
    return true;
15
}