[tomlagier]

This is part of the reason why the software industry's decision to use algorithm problems as time-bounded interview questions is so frustrating.

Right away, you have to make a choice between doing it the reliable way (brute force) and taking a gamble on being able to out-smart the problem and doing it the math-y way. This adds a ton of pressure, no matter which path you choose.

If you choose to start with brute-force, you're stressed that you look stupid because you don't know the trick. If you spend precious minutes looking for the trick, you're stressed because there's no guarantee you'll crack it in the given time.

I've just gone through a gambit of software interviews and this is the biggest thing that determines whether I'll enjoy solving a problem or not. If they start with "find an efficient solution" or "the data set is in the millions" or something along those lines, I know I'm doomed if I don't recognize the form of the problem. If they encourage me to get to a working solution first, and _then_ figure out the trick, I'll typically do well regardless of whether the question is familiar or not.