Palantir Technologies Software Engineer, interview questions

One of the algorithm questions I received was genuinely difficult (probably the hardest question I've been asked in any software engineering interview, in fact), but I don't remember the details quite well enough to replicate it here. Aside from that, the questions I was asked were all reasonable; however, I was a bit surprised when one of the interviewers spent several minutes speaking generally about my personal tastes/opinions regarding object oriented design, asking questions like, "what is your favorite design pattern?" Frankly, I really don't have a "favorite design pattern", and I felt a bit awkward answering these questions (which were posed with much enthusiasm).

The most difficult question for me was what I was interested in working on