Hi guys, hopefully this is an easy one for you.

Given a grid of nxn squares, where each square has an id, the first(top left) square has id 0 (so a 5x5 grid will have ids 0-24) like below:

I need to generate all diagonal solutions of length Y. So if Y is 3, then some of the solutions will be:

and

but obviously NOT

Any ideas how these solutions can be generated?