I applied online and was approached by HR to initiate the interview process. My next interview was a technical one, and I had hoped to clear it, but I failed.

The interviewer was helpful but failed to see my perspective. I initially approached the problem using an algorithm that I thought I knew, aiming for O(N) time complexity. However, I got confused. About 15 minutes into the interview, I asked whether I could use another approach, and this is when I started to get shaky.

I then proposed a solution in O(N^2) time. The interviewer asked to make it faster. Using hash tables, I improved the time complexity to O(N) with O(N) space. With a hint from the interviewer, I ultimately solved it in O(N) time with constant space, and then began writing the code.

During the entire 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 do differently, it would be to use the easiest approach to solve the question first. A positive start boosts confidence.

• Make sure to explain CLEARLY (using the correct terminology) how to tackle the problem.
• Embrace the fact that there is always a possibility of getting rejected.

So, blurt out whatever solution you think should work. There may not be 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).

A modification of the lowest common ancestor problem (bonus points if you answer using RMQs).