Idk if we should go with the fastest submission maybe set a time limit like a day 2 days week etcetc depending on how hard the callenge is then look at them all at once and see which is best. After it's all done someone could go in and explain exactly why that one is the better one therefore helping others learn better why things should be done a certain way etcetc:)
There's an idea. Some SwiftIRC channels used to do the same thing. Post a code challenge and have submissions, with the best, most efficient, fastest submission being the winner.