First, I had a 1:1 interview with a manager which went well with basic java questions. After that there was a take home coding challenge and a discussion of the code. Not really knowing what to expect I wrote the program and it worked fine. During the discussion with a different manager and an engineer it then became clear that the expectation was to write this small program with a heavily object oriented approach. Since on interviews you generally try and solve the problem as efficiently as possible I was not expecting this. I talked about why hashing made sense in the approach I took instead of using an array since the lookups were O(1) and the manager clearly didn't understand big O or hashing so he cut me off and immediately changed the subject every time I brought it up. They then asked a lot of the same questions the previous manager asked and didn't really seem interested in any explanation for the answers.