[dilap]

Dunno about hackerrank, but if you can consistently do well on topcoder algo or codeforces competitions, that's beyond having memorized stuff -- that's being genuinely good at problem solving, and having a broad base of knowledge about important algorithms. I'd be happy to work with you.

[banachtarski1]

Ditto on this. Someone who is passionate about algorithms outside of just memorizing interview problems i.e - they find problems like this - http://codeforces.com/contest/724/problem/G - interesting, usually have high problem solving and mathematical aptitude.

Perhaps I'd like to draw a distinction between genuine algorithms problems that you haven't seen before, and the really bad interview questions like "Find a cycle in a linked list". You'd be really hard pressed to find anyone who could solve the problem above.

Edit: To clarify, I would not remotely consider the linked Codeforces problem as a good interview problem.