For those who as I has wa3 or wa5 and don't understand why: 1) similar must be personal number, not passwords 2) personal number is decimal number 3) to get other password (i.e. calculate diffeence of passwords) we can ONLY change digit, we can't insert or erase digits like in personal number May be you don't have theese mistakes, but I spent a day to undestand it
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.