Citadel Coding Interview Questions
25 Citadel coding interview problems with full optimal solutions — 8 easy, 12 medium, 5 hard. Every problem ships with multiple approaches (brute-force first, then the optimal), complexity tables for each, company-specific tips on what an Citadel interviewer values, and a FAQ section.
Showing 3 problems of 25
- #4hardoccasionally asked
4. Median of Two Sorted Arrays
This is perhaps the most technically demanding standard LeetCode hard — O(log(min(m,n))) requires a binary search on partition points, not on values. Citadel asks it to separate candidates who understand binary search at a deep level from those who merely know it as a lookup pattern. Precise handling of odd/even total length and boundary conditions is non-negotiable.
- #239hardvery frequently asked
239. Sliding Window Maximum
Sliding Window Maximum is practically the interview problem for Citadel's trading systems domain — computing the rolling maximum price, maximum volume, or maximum order size over a fixed window is a core operation in market microstructure analytics. The monotonic deque solution is the expected answer; a sorted structure or brute force is insufficient.
- #1235hardoccasionally asked
1235. Maximum Profit in Job Scheduling
This problem is a weighted interval scheduling problem — find the maximum-profit subset of non-overlapping intervals. At Citadel, structurally identical problems appear in trade-off analysis: selecting the highest-value set of non-overlapping trading windows subject to latency budgets. It demands DP on sorted intervals with binary search, testing both algorithmic depth and implementation rigor.