I had a coding interview on CoderPad.

Just as some people believe college professors/lecturers who teach classes shouldn't have heavy accents, the same applies to interviewers. I had trouble understanding him, and it seemed like Facebook didn't care about who they used as interviewers; it felt as though they pulled someone randomly.

The interviewer was nice and knowledgeable about the question he was asking, but that was it. He also joined the call late, stating he had trouble finding a free room. This is super irresponsible, and I feel Facebook does not dedicate time to improving the interviewing process.

I'm glad they don't recruit at my university.

Write a function to check the validity of a binary search tree.