Implement C=|A-B| with inc,dec,jnz (A,B are non-negative)

Question

This is a question I saw in an interview :

A,B are non-negative numbers and you need to return C=|A-B| where you have only the following instructions:

Answer 1

Just decrement both in a loop until one of them gets to be zero. The other is obviously the result.

    inc a
    inc b      ; make sure input is not zero
loop:
    dec a
    jnz skip
    dec b
    mov eax, b ; return b as answer
    ret
skip:
    dec b
    jnz loop
    mov eax, a ; return a as answer
    ret