I've just achieved the ability to review close/reopen votes, and am trying to take this responsibility seriously. I was presented with the following question, and recommended that it be closed as too broad. Everything I've seen suggests that "here is my working code - please make it better" questions are not on topic at SO, and should be closed. But this was a test, and I apparently failed. The review queue admonished me for voting to close, saying there's nothing wrong with the question. That said, I really don't understand what I should have done differently in reviewing this answer!
Inverting an Order-Preserving Minimal Perfect Hash Function in Better than O(K*lg N) Running Time
Quick background on the question is that it presents a (perfectly fine) implementation of a specific algorithm, then states that it doesn't run fast enough, and asks for help improving the theoretical or implementation efficiency.
So my question is, what are there characteristics of good"please improve my code" questions that I should look for? Or is this audit question a bad one?
These related questions suggest the topic is murky at best: