A recruiter emailed multiple times asking for an interview with Pinterest.

I had a very bad interview experience. It was a one-hour technical phone screen. Here are the things I found with my interview experience:

1. Firstly, the interviewer called me 10 minutes late. Following time or apologizing when late is expected good manners, which the interviewer did not do.
2. When I started with a solution, he changed the problem to prove my solution was wrong and not scalable. (Come on, where do you find a scaling Sudoku?)
3. I made a mistake in computing complexity. (Interviews are never stress-free.) By this time, he had made up his mind that I am a bad engineer and started to criticize all points I made in the discussion, instead of helping me out or working with me. From this point onward, he kept pointing faults in my solution. You cannot judge a person based on one mistake; people make mistakes, and no one is perfect all the time.
4. He kept changing the problem, trying to prove my solution wrong or inefficient all the time.

I don't know what he was expecting from the interview. I did not write a single line of code. It was not a pleasure interviewing with Pinterest; the interviewer's attitude was really bad. The interviewer said it wasn't working out and dropped the call in 30 minutes. It sounded very rude to me.

Validate a Sudoku.