Meta Software Engineering New Grad interview questions

I applied online and was approached by the HR to initiate the interview process. My next interview was a technical one and I had hoped to clear it, but failed. The interviewer was helpful, but failed to see my perspective. I initially approached to solve the problem in O(N) time using an algorithm that I thought I knew. But I got confused and 15 mins in the interview, I asked whether I could use another approach. This is when I got shaky. I proposed a solution in O(N^2) time. He asked to make it faster and using Hash Tables, I improved the time to O(N) and space to O(N). And with a hint from the interviewer, I ended up solving in O(N) time with constant space (and then started writing the code). During the whole interview session, I accidentally kept confusing things (for instance calling a node,a root node because I was thinking in terms of sub-trees and recursively). This generally doesn't happen even when working under stress. I felt the interviewer grossly underestimated me, but I blame myself for that. If there is anything I would different then it would be to use the easiest approach to solution the question first. A positive start boosts up the confidence. Make sure to explain CLEARLY (using the correct terminology) how to tackle the problem. One more thing: embrace the fact that there is always a possibility of getting rejected. So, blurt out whatever you solution you think should work. There is not enough time to derive your approach. And be confident. Sometimes you can trick the interviewer into believing that you know exactly what to do, even when you don't (if you are close enough).

I applied online at the Facebook website. They came for a tech talk in my university. After a few days I got an email for a phone call. It wasn't a technical interview. Just a brief introductory call. After the call they setup a technical interview. The technical phone interview involves coding on colabedit.