I say "plain and simple" because IME people tend to overestimate the novelty of problems and underestimate the impact of "memorized" problems for solving new on

I say "plain and simple" because IME people tend to overestimate the novelty of problems and underestimate the impact of "memorized" problems for solving new ones. 3 months of studying for an interview, while extremely annoying, is generally speaking a pretty small amount of time needed to cover a field as vast and complex as DS&A. And yet it is more than sufficient for most because there's extremely little novelty in the problems being asked. They want you to solve classic algorithms, but either dont' want to tell you so or (more commonly, IME) don't realize they are asking classic algorithm problems and only think they are asking some novel problem. Even "simple" techniques will be impossible for a person to solve in an interview setting, and yet if they've seen it before the interviewer will think they are a brilliant programmer. Its a memorization game even though it doesn't directly look like one. IMHO.