I would be very surprised if you were asked about red-black trees or splay balancing at the two large tech companies I’ve worked for. That would be considered t

I would be very surprised if you were asked about red-black trees or splay balancing at the two large tech companies I’ve worked for. That would be considered too niche/specific to be a good interview question unless you were applying for a position which needed that particular knowledge. On the other hand asking to “invert” a binary tree is totally fair game. I attribute Max’s frustration partially to his interviewer not adequately explaining what “invert” means in that context though that would also partially give the answer since it’s IMO a very easy problem (though not a good one since it’s confusing).