Something is really wrong with their process. I answered the question PERFECTLY: optimal algorithm, clean code, and I did it fast. Everything was great. The interviewer was impressed too; he was previously a Research Scientist at Facebook. But then, I got a rejection the next day. I was SHOCKED! I have interviewed with many companies and I know what good performance is like.

Other people say the same thing about Snapchat too. It seems there is a generally agreed-upon opinion: even if you do well in their interviews, they are still very random.

Do not waste time interviewing with them if you are talented. People say that their interviewers are biased against certain kinds of people and will reject them no matter what. No feedback is ever shared, so they are off the hook.

Randomly shuffle an array.