Dropbox challenge
The first one is a knapsack problem: http://en.wikipedia.org/wiki/Knapsack_problem
The third on is Zero-sum problem: http://en.wikipedia.org/wiki/Zero-sum
Nor sure about the second one. Anyone who knows?
Ha, the first one is cute. It's stolen almost directly from some CS competition training problems I did back in high school.
I saw it and _knew_ I'd seen it before. ;)
(edited to remove the name of the competition, since it turns out some answers are Googleable :-\)
1st one just screams Genetic Algo. Maybe thats just a case of "When you have a hammer..." though. I don't see any CPU/time limit though so maybe there is a proper solution.
This reminds me of what Facebook just recently started doing. I remember reading an article about how Facebook's plan failed though (regarding the hackathon)
"mexican-coke". That doesn't sound very legal...