There were two phone interviews before the onsite interviews. I made it to the second phone interview.

The goal of the first interview seemed to mainly be about getting a good feel for the candidate. The interviewer asked me about past projects I had worked on and any problems that I had to overcome.

The second phone interview was a technical test. The interviewer asked me technical questions, many of which I had found online from past candidates.

The twist was how well you knew the subject, and not necessarily whether or not you got the correct answer. This interviewer's tactic was to continuously ask me, "How can you make that solution better?" after each question.

He told me I got most answers correct, yet I stumbled each time he asked me to find a better solution. The stumbling, I feel, kept me from the onsite interviews.

How can you tell if a linked list is circular (goes on forever because it connects to a previous node)?