Background and work related questions followed by coding portion. The coding portion I solved using a fixed size array that wrapped around. The interviewer was adamant that the performance was O(n), but it was O(1) because it wrapped around with a running index. He later agreed with me after realizing he was wrong and ran some tests. He asked me to change it to what he wanted which was a growing linked list up to size n instead. His reasoning was that an array was too big to allocate for and the linked list was better. I went with his "desired" and "correct" solution. In my head, I'm thinking: "Hold on now. You're telling me to grow a linked list up to size n instead of a fixed array of size n? you didn't specify that we were running multiple instances and can't expect size n for every instance..." I guess it was not clear to me that he had a specific use scenario in mind when he asked the question. I did not pass because I did not conform to the answer he knew.