My only gripe is that the engineer I interviewed with first told me not to worry about any language API limitation, but during the interview, told me that doing something would violate a language construct and I couldn't continue with that part of the solution. I agreed because I wasn't positive if the API would allow it, but in any case, I wasn't trying to do some black-box magic 'this function sorts an array in constant space' kind of thing, so it shouldn't have been alright. Turns out that what I was trying to do was perfectly legal within the API, so I really didn't violate anything. Anyway, that bad info forced me to write a solution in O(nlog(n)) space when I could have done it in O(n).