This is true, but I doubt they are just looking to see if you can find the answer. From my experience, they are much more interested in seeing how you approach

This is true, but I doubt they are just looking to see if you can find the answer. From my experience, they are much more interested in seeing how you approach the problem and can analyze your own algorithm's performance. I think if anything the latter is more important than coming up with optimal solution. I've definitely encountered questions where I wasn't familiar with a certain topic, and usually they'll realize it and just give me hints. I did also have interviewers who just watched me struggle though.