Jane Street Software Development Engineer Intern interview questions

The interview process began with a conversation and resume drop at a career fair, but I was told that applying online would have been the same. A couple weeks later, I received and email asking for availabilities in a two-week window. The first interview lasted about 1 hour 15 minutes. Interviewer was very friendly, and passionate about his work. It was a phone interview with live coding on code.stypi.com. Questions were straightforward. After a quick intro we went straight into the first question topic, power sets. After question, given an alternate solution involving binary strings. Remaining 30 minutes or so devoted to Q+A. Heard back in 15 minutes (next round) Second interview was also a little over 1 hour. Most of the time devoted to a single coding question (it was up to me to break it into parts). Key idea was to break an abstract idea into codable elements, show your thinking process, and make a useable interface. Heard back the following week, no offer. Both interviewers were every friendly and did a good job at maintaining a moderate-to-high level of difficulty (occasionally commenting "are you sure?", "um", or "okay" to hint at whether or not I was going in the right direction). First interview was moderate, second quite difficult. Both questions were interesting and unique as far as I could tell.