Radix Trading Interview Questions
The real Radix Trading quant-interview problems candidates report — coding, probability and linear algebra — each with a full worked solution.
Inside the Radix Trading interview
Radix Trading is a Chicago-based quantitative proprietary trading firm and one of the most selective shops in the industry — its interviews run deep on probability, clean algorithmic coding, and the math (linear algebra, combinatorics) that the quant-research loop is built on. This set collects the problems candidates actually report, each with a full worked solution and, where known, the month it was last seen.
What they test
The largest block is probability and brain-teasers — often geometric or symmetry-driven. Around it sit algorithmic coding (classic data-structures-and-algorithms) and a math core of linear algebra, combinatorics, optimization and statistics. Radix favours depth over breadth: fewer problems, but each one rewards a rigorous, clean argument.
The recurring shapes
You will see geometric probability (a random chord's length, a triangle from three uniform points), symmetry and parity arguments, weighing and poison-identification puzzles, and canonical coding (DP, two-pointer, pattern matching). The move is almost always to find the symmetry or invariant before you compute.
How to approach
Set the problem up cleanly, look for symmetry or an invariant first, and only then reach for calculation. On a coding problem, pin the right data structure or DP state before writing a line. Radix interviewers probe how you reason, not whether you recall a formula.
49 problems, leaning medium-to-hard (27 medium / 18 hard / 4 easy). The dated ones carry the month they were last reported, so you can see the set is current — not recycled folklore.
Radix Trading coding questions (17)
- Summing an Array with Vastly Different Magnitudes Accurately
- Second Largest with Minimum Comparisons
- Implement a Reference-Counted Smart Pointer in C++
- Fixed-Buffer Memory Allocator: rdx_malloc and rdx_free
- Maximum Profit with Two Transactions
- Order Management System with Price-Time Priority Matching
- Order-Statistics Tree
- Segment Tree with Lazy Propagation for Range Add and Range Min
- Union Area of Axis-Aligned Rectangles
- Russian Doll Envelopes (2D LIS)
- Largest Centered Cross in a Matrix
- Task Scheduler With Dependencies and Earliest-Start Times
- Wildcard Pattern Matching
- Longest Subarray With Sum at Most K
- Longest Subarray With Sum K
- Largest Subset With Nonzero Bitwise AND
- Design a Sparse Matrix Class With Add and Multiply
Radix Trading probability questions (10)
- Random Chord Length on a Unit Circle
- Triangle From Three Uniform Random Sides
- Identifying Poison With Multiple Tasting Rounds
- Deriving Stirling's Approximation by Turning the Sum into an Integral
- Divisibility of Dice Sums by 6 and 7
- Perfectly Balanced Dice Rolls
- Arrival Order Probability Across Cities
- Even vs. Odd Heads: Does Symmetry Force Fairness?
- Extinction Probability of a Bacterium
- Posterior Probability with Symmetric Urns
Radix Trading linear algebra questions (6)
Radix Trading combinatorics questions (5)
Radix Trading optimization questions (4)
Radix Trading statistics questions (4)
Radix Trading stochastic processes questions (2)
Radix Trading regression questions (1)
Radix Trading interview FAQ
What kind of questions does Radix Trading ask in quant interviews?
Candidates most often report coding, probability and linear algebra questions. This page collects 49 of them, 15 stamped with the month they were last reported — each with a full worked solution.
How hard are Radix Trading interview questions?
The set spans 4 easy, 27 medium and 18 hard problems. Most sit at medium difficulty — solvable in a few minutes with clean reasoning — with a harder tail that rewards knowing the canonical tricks.
How do I prepare for the Radix Trading quant interview?
Work through this set by topic (use the sidebar), starting from your weakest area. 5 problems are free to open with their full solution, so you can judge the quality before anything else. Then walk the full Radix Trading interview guide for the round-by-round funnel and the online assessment.
Are these the actual Radix Trading interview questions?
They are built from candidate-reported Radix Trading questions. We rewrite each prompt for clarity and author the worked solutions ourselves — we don't claim the wording is verbatim, and we never invent questions or recycle generic lists. 15 of 49 carry the month they were last reported.