Contacted through the school's co-op program. I had a phone interview with pretty standard coding/algorithms brainteasing questions. I crushed the algo questions, but needed some help on a weird graph theory question he threw at me.

The interviewer seemed a bit odd, asking me at the beginning if I would 'have any problems' working on their product, as if they were doing something morally wrong.

After the interview, he asked me to submit code for one of the algo questions we had discussed. What really bothered me was that, after I submitted the code, I never heard back from him or anyone at the company. Not so much as a confirmation he had received it, just a rejection in our ranking system a few weeks later.

A graph theory question relating to whether it is possible to 2-colour a 2-dim plane divided by an arbitrary number of lines.