just finished the citi OA last week so this is fresh. documenting everything because when i searched i found posts from 2022 that seemed outdated.
platform: HackerRank. you get 90 minutes for two problems. one SQL question might show up depending on the role (it did for me, TTS analyst track).
difficulty: honestly medium leetcode. not easy but not hard either. the graph problem i got was something like finding connected components in a transaction network. the string one was about matching transaction IDs with some pattern. neither was a trick question, just solid fundamentals.
what tripped me up: the HackerRank test cases include some large inputs. my naive solution for the graph problem timed out on 2 of the 8 test cases. i wasn't expecting that with a medium-level problem. lesson learned: think about the O(n log n) solution, not just something that gets the right answer.
what i heard from others: someone in my university's slack said they saw a DP problem on theirs. so the problem set rotates. cover arrays, hash maps, graphs, maybe one simple DP. probably don't need to grind hard problems.
how long until recruiter follows up: 8 business days for me. one person i know heard back in 4. seems like they batch reviews.
if you're a new grad targeting the tech analyst or ICG tech track, this is the gate. pass this and you're into the phone screen. not trying to sugarcoat it but it's definitely passable with a few weeks of leetcode mediums.