Time and time again, I try writing recursive solutions for problems on this website, only to be greeted with "Time limit exceeded," when they most definitely work compiled on my own machine, and often don't have a noticeable performance penalty compared with the non-recursive solutions I'm consequently forced to write. It's seriously a bad practice to enforce on the part of the website, that recursion is never the performant answer, and it's plainly misleading. If the platform doesn't allow more than say 10 nested stack frames in an execution path, that should be plainly stated. Moreover, there are some problems where a recursive solution is simply the most performant, readable, and idiomatic approach. Take for example problem 65, Valid Number. The problem obviously calls for an LL parser to be written to solve the problem, yet enforces us to write such a parser without any recursion, which is just absolutely the worse approach.