Citadel Onsite - 7yoe | bad interview experience
Summary
I had an onsite interview at Citadel, which was somewhat marred by the interviewer's late arrival and demeanor. I was asked a challenging problem involving merging sorted streams with stateful aggregation, which I had fortunately practiced before.
Full Experience
This one is a blend of “merging sorted streams” + “stateful aggregation”.
What I did: Min-heap over K feeds (timestamp as the key) so events are always chronological when you pop. Track a running cumulative price (initial price = 0) and output absolute prices, not deltas.
discussed some edge cases and how i would handle them with the interviewer: multiple feeds emitting at the same timestamp negative deltas empty feeds / single feed
There's a similar problem here I practiced so I had plenty of time: https://offerretriever.com/questions/10
The interviewer actually arrived super late, so it was kind of a bad interview experience. He also feels super tired and stressed and didnt' really want to be there or talk to me. Luckily I've practiced this problem before, and was able to finish the problem.
Really hard to say what the interview result will be.
Interview Questions (1)
Merge Sorted Streams with Stateful Aggregation
The problem involved merging sorted streams and performing stateful aggregation. I needed to use a min-heap over K feeds, with the timestamp as the key, to ensure events were always processed chronologically. The task was to track a running cumulative price (initial price = 0) and output absolute prices, not deltas. Key edge cases discussed included multiple feeds emitting at the same timestamp, negative deltas, and handling empty or single feeds.
Preparation Tips
I had practiced similar problems before, which allowed me to complete the problem efficiently despite the challenging interview circumstances. I also specifically practiced a similar problem available at https://offerretriever.com/questions/10.