Adjacent number algorithm grouper

Question

By which I mean this:

Given the input set of numbers:

1,2,3,4,5 becomes \"1-5\".

1,2,3,5,7,9,10,11,12,14 becomes \"1-3, 5, 7, 9-12, 14\"

This is

Answer 1

Looks clear and straightforward to me. You can simplify a bit if you either assume the input array is sorted, or sort it yourself before further processing.

The only tweak I'd suggest would be to reverse the subtraction:

int difference = (current - lastNumber);

... simply because I find it easier to work with positive differences. But your code is a pleasure to read!