[gjm11]

Well, FWIW, when I've asked people "write me code to reverse a list", I've simply assumed that unless the candidate is a real superstar it'll probably take them a while to get to a working solution, and I'm happy to give them some help along the way. I completely agree that an interviewer who expects a correct solution within a few minutes (even to a relatively simple problem like that one) is being dumb and helping to make the world a worse place.

As for "aha! brilliance", the trouble with that is that the variance is so large; someone very good may well take a while, and someone not so good may well happen to get there quickly.