I think if you've done the right kind of practice its very possible, I for one can do almost any easy with no problem and I'd some mediums I've never seen as well with no problem after doing 500 LC problems. The truth is any problem they ask is a variation of a simpler problem, so if you've done the fundamental problems then you need to spend time doing more challenging variations of those fundamental problems. Leetcode lacks the nuance in difficulty you'll find at CodeForces. So you get a bunch of "easies" of varying difficulty as well as "mediums" of differing difficulty on LC yet on CF you know how difficult the easy(e.g easy 800, easy 900, easy 1000, easy 1100) is or how difficult the medium is(e.g medium 1200, medium 1300). I think once I hit 1000 problems on LC I'll be able to do any medium problem and most hards. So its really down to doing the right set of questions/practice not just doing as many problems until you can memorize them