I'm not writing down the question verbatim since that is really unfair to the interviewer and the company. A coding question related to graphs. I really liked the question. It was difficult, and unless you implement graph traversals on a daily basis, this question will be difficult. I think given the problem and an hour to 90 minutes of quiet time, I could have implemented this since the last time I implemented graph traversal was about a year ago. Make sure you practice your graph traversals. The interviewer was really nice. Although, having checked their profiles on LinkedIn, they are overly proud of having a few PhDs in their group. :-)