I tend to ask what I think is a rather simpler question in most interviews: find the sum of the two largest (most positive) numbers in an array of arbitrary integers. Consider the efficiency of your solution for very large arrays.<p>It is amazing how many seemingly knowledgeable, intelligent people cannot do this. And the vast majority of those who do, do it by sorting the array, efficiency be damned.<p>Actually, I'd like a bit of feedback here. Is this something any decent developer should be able to do with ease? Should it be obvious that it can be done much more efficiently without running a sort on the array? Admittedly there are minor gotchas with things like the initial conditions, but still, I've been flabbergasted by how few people can even get close to a solution, let alone a bug-free and efficient one.