The interviewer was a Senior engineer, and he was 5 minutes late. He started off explaining what his team does — since this was a direct match on background with an infra team, I spent about 3-5 minutes introducing what I used to do on my previous team, and he asked me one question about it. After this intro segment, there was about 45 minutes left.
The actual interview started. It was a known question from the prep bank: Find Optimal Commute. I proposed using Dijkstra's algorithm and walked through the approach along with the time/space complexity. The interviewer hinted that this problem could be optimized further and that Dijkstra wasn't really necessary. I then proposed that for each given mode, I could use a standard BFS to compute cost/time and compare them at the end, and briefly went over the time/space complexity for that. The interviewer said that made sense and told me to go ahead and code it. This discussion part took 15 minutes.
I started talking through it while writing code. The BFS part went pretty smoothly and I got it finished. When I test-ran it there were a few small int/str bugs, which I fixed quickly.
But at the end, when comparing the cost/time across each mode, I needed to handle duplicates, and the interviewer said I couldn't just sort — it had to be O(n). My brain completely blanked for a good while and I couldn't figure it out, even though it's actually really simple!! In the end I said time was running short, and asked if I could skip the duplicate handling for now and just run the full code. He said that was fine. I hand-wrote a test case and it ran successfully. By then there were only 5 minutes left.
The interviewer said there were only 5 minutes left and asked if I had any questions for him. I asked whether on-call was rough and whether there were any new projects this year. He said on-call used to be pretty heavy, and when it came to new projects he thought about it for a while — from what I could tell, this team is mostly operations-heavy. I mentioned that on-call on my previous team was also heavy, blah blah.
The interview was at 11am, and by 3pm the same day I'd already gotten the rejection email along with a one-year cooldown... I'm numb. Honestly I don't really know why I got rejected, because other than getting a bit stuck near the end, the rest of the communication and coding went pretty smoothly.
I hadn't interviewed in 5 years!
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