Candidates who interviewed at Citadel in 2024 and 2025 describe the same rounds: a HackerRank OA with two coding problems, a first technical interview with a short resume chat and one LeetCode medium, a superday of three back-to-back technical interviews, and then team or project matching with a behavioral interview and one more technical round. Reported questions were dynamic programming (a Frog Jump variant), sliding-window strings, settling debts with fewer currency transfers and counting job schedules.
Most reports end without an offer, at the OA or the first technical round. The one intern who got an offer said running, optimal code mattered more than code style.
Citadel interview process round by round
| Round | Duration | What candidates reported |
|---|---|---|
| HackerRank OA | About 66 min | Two LeetCode medium/hard problems; difficulty reports range from “relatively easy” to “very difficult” |
| First technical | 45 min | Introduction, resume questions, about 15 minutes of behavioral in one report, then one LeetCode medium |
| Superday | 3 x 45 min | Back-to-back coding: DP, implementation, class design |
| Team / project matching | 1+ rounds | One behavioral and one hard technical; OS and networking for some teams |
| Leadership interview | 1-2 calls | Mixed technical and behavioral with a senior engineer |
Citadel interview reports from 2024-2025
These are self-reported write-ups, mostly from Taro (jointaro.com). Each is one candidate’s account.
- Software engineering intern, New York (August 2024, accepted offer). 66-minute HackerRank OA with two LeetCode medium/hard problems, a 45-minute phone interview (15 minutes behavioral, 30 technical), a superday of three back-to-back technical rounds, then team matching with one behavioral and one very challenging technical interview.
- Software engineer intern, New York (February 2025, no offer). Found the OA very hard and advanced with 9/15 and 5/15 test cases. Technical round: smallest substring with non-repeating characters. Superday: three technical rounds including a Frog Jump DP variant. Project matching covered OS and networking and differed between Citadel and Citadel Securities.
- Associate software engineer, United States (April 2025, no offer). Automatic HackerRank OA after applying, which the candidate called very difficult compared with other companies; the advice was that a perfect score is needed.
- Software engineer intern, New York (September 2025, no offer). OA arrived two days after applying and felt like LeetCode easy-to-medium; one problem counted the ways to assign n jobs to m intervals under a rule about consecutive intervals. Rejected about a week later.
- Software engineer intern, New York (October 2025, no offer). OA described as reasonably difficult, a first round a few days later with similar DSA questions, then a superday of three interviews about two weeks later. One reported question: reduce currency transfers.
- Software engineer intern, United States (November 2025, no offer). First technical round of an introduction, resume questions and one LeetCode medium. The candidate felt it went well but was not invited to the superday.
Detailed interview experiences
Experience 1: SWE intern, New York, offer (2024)
Profile: Undergraduate applying for the summer internship.
Online assessment: HackerRank, 66 minutes, two problems at LeetCode medium/hard. The candidate said the OA plus resume decided who advanced.
Phone interview: 45 minutes. About 15 minutes of behavioral questions, including why Citadel and what they wanted to do the following summer, then 30 minutes of coding.
Superday: Three back-to-back technical rounds, mostly LeetCode medium or easier hard, centered on implementation and class design.
Team matching: Hiring managers chose whether to interview the candidate. It was not standardized: one behavioral interview and one technical interview the candidate called very challenging.
Result: Offer accepted.
Takeaways
- What decided it: Optimal solutions with running, tested code in every superday round.
- Common fail: Spending time on code style while leaving the solution untested.
- How to practice: Three 45-minute problems in a row with your own test cases, then a short “why Citadel” answer said out loud.
Experience 2: SWE intern, New York, superday and project matching (February 2025)
Profile: Summer intern candidate.
Online assessment: Very hard by the candidate’s account. They passed with partial scores: 9 of 15 test cases on the first problem and 5 of 15 on the second.
Technical round: LeetCode-medium style; the question was the smallest substring with non-repeating characters.
Superday: Three technical rounds with medium and hard problems. One was a dynamic programming problem described as a Frog Jump variant with a twist.
Project matching: One or more rounds on operating systems and networking concepts, plus LeetCode problems depending on the interviewer and project. The candidate noted it differed between the Citadel and Citadel Securities tracks.
Result: No offer, rated a positive experience.
Takeaways
- What decided it: Partial OA scores were enough to advance; the cut came later.
- Common fail: Strong DSA but thin OS and networking for team matching.
- How to practice: Review processes, threads, virtual memory and TCP basics before the superday, not after.
Experience 3: SWE intern, New York, superday after a fast OA (October 2025)
Profile: Summer intern candidate.
What happened: An OA the candidate called reasonably difficult, a first-round interview a few days later with DSA questions in a looser format, then a recruiter invitation to a superday of three interviews about two weeks after that. The one question they listed was “reduce currency transfers,” a debt-settlement problem.
Result: No offer, rated positive.
Takeaway: The gap from OA to superday can be under three weeks, so do your superday-length practice before you submit the OA.
Experience 4: Associate SWE and interns cut early (2025)
Profiles: An April 2025 associate software engineer, a September 2025 New York intern and a November 2025 US intern.
What happened: The associate engineer received an automatic HackerRank OA, found it harder than other firms’ tests and did not advance. The September intern found the OA easy-to-medium, including a counting problem on assigning jobs to intervals, but was rejected about a week later. The November intern passed the OA, had an introduction, resume questions and one LeetCode medium, felt it went well and was not invited to the superday.
Takeaways
- Common fail: Assuming a solution that passes visible tests is enough; reports say hidden test cases and full correctness decide the OA.
- How to practice: Write brute-force checkers for counting and DP problems and compare outputs on random small inputs.
Experience 5: Quant candidates at Citadel Securities (2025)
Profiles: A quant trading superday candidate in October 2025, a London quant research candidate in November 2025 and a Sydney trading candidate in March 2025, as collected by Quantt.
What they were asked: The October 2025 superday asked the stones-in-a-bag problem: four stones each black or white, two draws both black, what is the chance the next is black. The London research candidate was asked how a series Y moves if a correlated series X rises two basis points. The Sydney candidate had two technical interviews on probability and game theory.
Takeaway: For trading and research, state your assumptions (the prior, stationarity of the relationship) before giving a number. The stones question has different answers under different priors.
Citadel interview questions that come up often
Coding
- Smallest substring with non-repeating characters (sliding window)
- Frog Jump DP variant
- Reduce currency transfers between people (debt settlement)
- Count ways to assign jobs to intervals under an adjacency rule
- A harder Parallel Courses variant and a sliding-window mean (2025 intern reports via Quantt)
Fundamentals (team matching)
- Operating systems: processes, threads, memory
- Networking concepts
- C++: iterators, memory management, std::variant, std::vector (experienced hires)
Quant research and trading
- Stones in a bag with an unknown black/white split
- Regression of one correlated series on another
- Dice, coin and Fermi estimation questions; market making
Behavioral
- Why Citadel?
- What do you want to do next summer?
- Walk me through a project
Citadel behavioral questions in these reports
The 2024 offer report had about 15 minutes of behavioral questions in the phone screen, and team matching included a behavioral interview. Sample answers for why Citadel, project walkthroughs and pressure questions are on the Citadel behavioral interview questions page. The full round structure, pay and technical answers are on the Citadel interview questions page.
Citadel interview tips from these reports
HackerRank OA
- Two problems in about 66 minutes; partial scores advanced one February 2025 intern, while an April 2025 candidate said only a perfect score works.
- Test counting and DP answers against a brute force on small inputs.
Superday
- Three 45-minute coding rounds back to back, LeetCode medium to hard.
- Optimal, running code mattered more than style in the 2024 offer report.
Team matching
- Not standardized: a behavioral interview plus a hard technical one.
- OS and networking came up for at least one 2025 intern.
Sources
- Taro: SWE intern, New York, August 2024 (offer)
- Taro: SWE intern, New York, February 2025
- Taro: associate software engineer, United States, April 2025
- Taro: SWE intern, New York, September 2025
- Taro: SWE intern, New York, October 2025
- Taro: SWE intern, United States, November 2025
- Quantt: Citadel and Citadel Securities interview process and reported questions
- Leadership interview description: an October 2025 Glassdoor review of a Citadel software engineering loop
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