TPS.
Solved the problem in probably 20-25 minutes. The rest of the time was spent "optimizing" the solution to cater to a really smart, rude, and naive interviewer.
Instead of focusing on how to improve space complexity or the algorithm itself, I think they are focusing on how good, artsy data structure(s) you can come up with. (Interviewer hints to use a hashmap of lambda functions is easier to use over plain simple pattern matching).
This is termed as "collaborative" engineering culture, I guess. Be aware!
RPN
The following metrics were computed from 16 interview experiences for the Opendoor Software Engineer role in San Francisco, California.
Opendoor's interview process for their Software Engineer roles in San Francisco, California is very selective, failing most engineers who go through it.
Candidates reported having negative feelings for Opendoor's Software Engineer interview process in San Francisco, California.