[helpmehn]

If, by "non-trivial," you mean NP-hard, I agree. :-)

[ikarous]

I was trying to be vague so as not to give hints to those interested in trying the challenge. Evidently, I am utterly guileless.

[helpmehn]

Given the number of combinatorial optimization problems that are NP-hard, I don't think that gives anything away to anyone who doesn't already know what you're talking about.