[hn_throwaway_99]

Couldn't disagree stronger with this. In fact, I love this problem, in that it gets rid of most of the complaints about engineering tech interviews: (1) it's "real world" (for the job in question), (2) can be reasonably done in the time alotted, (3) involves a task that is most common for developers (modifying existing code), (4) shouldn't require extra preparation.

I have seen many times where a user can actually explain the solution to a problem, but the translation from algorithm-to-code is extremely slow, or not done correctly at all. There is real skill in being able to output code quickly, even if you already know the English-language description.