I took an OA with Jane Street. It was scheduled to be a 1hr interview. Overall, the interview seemed like it had ended the moment the interviewer showed up. They were slightly late and unprepared, which is fine, but also seemed like they didn't want to be there in the first place. After the initial hurdle of getting things to work, we got started. I asked if we should do a round of intros to get to know each other's backgrounds. The interviewer refused. We jumped straight to the question. It was a LC easy which was quite surprising. They stated that correctness is very valuable in the implementation. I implemented a minimal solution using a less commonly used functional programming approach compared to the textbook imperative approach; the interviewer initially didn't fully understand my solution and subjectively critiqued it, even though again, they didn't fully understand it. I tried explaining it using FP concepts, and how this is the go-to way of approaching such problems in Haskell for example, but the interviewer seemed to brush that off. I also stated multiple other ways we can approach the problem using FP and non-FP ways and how they are related. Generally speaking, if you expect a collaborative interview, both parties should know each other's backgrounds; otherwise, it is a guessing game of finding out how to communicate with the person in front of you, using which terminology and what degree of granularity. After explaining things, the interviewer got convinced with the approach and immediately ended the session. I asked if I could go through the solution from a high level and discuss things such as trade-offs; the interviewer didn't want to. At this point we were only halfway into the interview even with the late start. I was given the opportunity to ask a few questions, which I did. The interviewer again seemed disinterested and was generally dismissive of most of my questions to say the least. This interview was a complete joke and a waste of time for me and the interviewer.