Applied online, got an automated email to schedule a phone call with a recruiter. He asked what kind of games I like, currently playing, if I like League, why, and why I want to work at Riot. He also asked what I wanted to work on at Riot. Second email came to schedule a technical interview with an engineer over the phone for an hour. The email came with a bunch of suggestions of CS topics to cover. Almost none of it showed up in the interview.

Two engineers were hard to hear on their conference phone, I repeatedly had to ask multiple times for them to repeat what they were saying. They asked questions about two datastructures types and when you would use one vs. the other. Then they asked what was a hard technical challenge I faced at my current job at another game studio. We spent a lot of time on that, perhaps too long, because by the time we got to the technical question it was late into the call - about 30 minutes or so. I just kept answering his questions as best I could understand.

They asked me a technical question I had been asked before. I previously successfully worked out and was hired into the company that asked it. Thus I was able to tell them nearly three different solutions and explain why they would work. By the time we got to the actual programming, there was about 5 minutes left. I choked coming up with some conditional off the top of my head. The interviewer decided to end the question when I goofed it. I got one function call in before he called time, which is really silly. They gave me 5 minutes to ask them questions about Riot.

They sent me a follow-up email declining me two or so days later. Then scheduled another phone call for feedback. I was told that I had to come up with a solution in code to move on, despite the rest of the interview going well. It was cool they followed up after with why, but I feel they kind of missed the point of an interview. Not my loss, I know I've solved that problem before. It's just a shame that I was hardly "interviewed" by that point on my programming. They said I got all the other questions right so not sure why we couldn't progress a bit further.

Describe a situation to use a HashSet as opposed to a BST.