Why is answer 0 0 2 1 ?

Yes, why 0 0 2 1???

Edited by author 03.11.2009 21:14

Because
1) There are 0 pairs of employees whose pin-codes are different at 1 position.
2) There are 0 pairs of employees whose pin-codes differ at 1 position.
3) There are 2 pairs of employees (1 and 2, 1 and 3) whose pin-codes differ at 3 positions
4) There is 1 pair of employees (2 and 3) whose pin-codes differ at all 4 positions.

Thank you melkiy
I have AC now+)

Edited by author 04.11.2009 14:15