I don't think there's much difference either way. In both cases, a candidate gained a large advantage in a way that tells you very little about their ability.

I don't think there's much difference either way. In both cases, a candidate gained a large advantage in a way that tells you very little about their ability. I think this is why contrived questions gained popularity in the first place - they eliminated noise due to candidates randomly having solved similar problems before (that and "real life" problems usually can't be explained and solved in 1 hour).