DRW Coding Interview Questions
25 DRW 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 DRW interviewer values, and a FAQ section.
Showing 8 problems of 25
- #1easyvery frequently asked
1. Two Sum
DRW uses Two Sum as a rapid-fire calibration question — they want to see the hash-map instinct fire in under 30 seconds. At a firm where order-matching engines process millions of ticks per second, the difference between O(n) and O(n²) lookup is not theoretical.
- #20easyfrequently asked
20. Valid Parentheses
DRW surfaces Valid Parentheses as a proxy for expression-tree reasoning — a skill that maps directly to parsing FIX protocol tags, validating order-routing rule expressions, and interpreting nested config syntax in trading systems.
- #21easyfrequently asked
21. Merge Two Sorted Lists
DRW uses Merge Two Sorted Lists as a building block — it is the O(n+m) merge step inside merge-sort, inside merge-k-sorted-lists, inside order-book consolidation. Get this right cleanly and quickly; interviewers use it to see pointer discipline before escalating to the k-way variant.
- #53easyfrequently asked
53. Maximum Subarray
DRW frames Maximum Subarray as a drawdown-analysis problem: find the contiguous period with the maximum cumulative return. Kadane's algorithm is the expected answer — and DRW will ask you to extend it to track the actual window start and end indices, then to compute it over a live return stream.
- #66easyfrequently asked
66. Plus One
DRW uses Plus One to probe carry-propagation logic — a primitive that appears in arbitrary-precision integer arithmetic, price tick increments, and sequence-number rollover in market-data protocols. The edge case of all-nines reveals whether you think about overflow by default.
- #70easyfrequently asked
70. Climbing Stairs
DRW uses Climbing Stairs to probe whether candidates recognize Fibonacci-structure recurrences and immediately space-optimize. The follow-up — counting paths under a step-size constraint — mirrors the combinatorics in option-path counting and lattice models.
- #121easyvery frequently asked
121. Best Time to Buy and Sell Stock
At DRW, this is not just a coding question — it is a trading question in disguise. The optimal-entry / optimal-exit framing maps directly to how DRW thinks about position entry timing in its proprietary strategies. Expect the follow-up to jump from O(n) code to expected-value maximization under uncertainty.
- #206easyfrequently asked
206. Reverse Linked List
DRW asks Reverse Linked List to test pointer manipulation under pressure — a skill that maps to low-level ring-buffer and lock-free queue implementations used in market-data feed processing.