Everything was great until I had the phone interview. It was by far the worst phone interview experience I've ever had.

• The interviewer did not speak English well and refused to move to a more quiet location.
• The problems were easy, and after getting solutions, the interviewer asked me to make impossible optimizations. It is impossible to do this problem in O(1) space; in fact, the interviewer's own solution runs in O(n) space.

But apparently, I had to do this, even though I had a working O(n) space and time solution 5 minutes in. If my interviewer does have a working O(1) solution for this, someone should award him the Turing Prize.

leetcode