Filled out a coding challenge, got a call back. The interviewer started by asking if I was busy, and if I found this stuff boring. Then he asked me to reverse an array on a code sharing website. After that he asked how I would change phone numbers on a website. He sounded really angry that my solution didn't include regular expressions, and even more angry when I asked what they were (because I wanted to learn). Maybe he was stressed out over doing interviews constantly, I don't know. Either way, I've never heard an interviewer get mad at me before. I didn't get the offer, but maybe that's for the better.