I had my first round interview on campus with BCG. As someone with an advanced non-business degree, I knew I was going to be a somewhat unusual candidate. Accordingly, I spent months preparing for the case interviews and general fit questions. My interview was the final one of the day. Unfortunately, it quickly became clear that my interviewer had zero interest in being there at that point. He was extremely short and rude throughout the interview. The case he gave me was a straight numbers problem (which I didn't realize until part of the way through). It was surprisingly difficult, and I struggled both with keeping the numbers straight and dealing with the pressure of the interviewer's attitude. The second interview went better. The guy was tired, but nice, and the case was somewhat more conventional. However, I knew by then that it was already a lost cause, so I just kind of struggled through it and got out of there.