I had a phone interview with LinkedIn. The interviewer had a heavy Chinese accent, even though he had been with LinkedIn for over 10 years.

The call started on an awkward note when I walked my interviewer through my professional background. I had spent 10 minutes talking about it and was eager to start the coding part, but the interviewer insisted on spending yet another 10 minutes on my background. In my experience, phone interviews are focused on writing code, but apparently not for this gentleman.

When we finally moved to the coding part, the questions themselves were fairly easy. However, the interviewer had a hard time understanding the difference between HashMap's contains and add methods' time complexity. Since both are constant time operations, I opined that the difference between using one over the other was purely semantic. The interviewer did not seem to understand what that word meant and asked me why I thought using add was better than using contains. We argued about this for over 5 minutes.

Finally, when I had a working implementation, the interviewer did not seem convinced it would work, so I had to map out the entire function call stack for him on a shared screen. At the end, he begrudgingly accepted that the code looked okay.

Lowest Common Ancestor in a Binary Tree, Given Two Nodes:

1. If the node class had a parent pointer.
2. If the node class did not have a parent pointer.