Hudson River Trading Interview ProcessTier 0
HRT is famous for some of the hardest mental-math and probability questions in the industry. Coding screens are short and exact; onsites are conversational but mathematically demanding. Expect to derive results live on a whiteboard, often without a calculator.
Online Assessment
HRT's OA is role-dependent and recycles a small, stable pool that leans classic-algorithmic and simulation rather than quant-math. The flagship Algo Developer OA is a ~150-minute, 3-problem set from a current canon (Fancy Number, a 2048 / Reversi board simulation, an N-ary tree problem); SWE and intern roles get shorter CodeSignal / HackerRank coding sets. Quant Researcher candidates take the same SWE / Algo-Dev OA - only the Quant Analyst screen is separate (short, C++-only). Heads-up from an August 2026 sitting: 2 of the 3 problems still came from the known pool with trivial modifications, but the third was new - a tree construction / manipulation problem solved with DFS (reported as 'merge trees'), described as the hardest on the set. Drill tree building, tree merging, and DFS traversals alongside the canon below.
Practice this round 18 problems ProThe flagship OA and the single biggest cut: three problems from a stable, recycled canon (recent posts report 'all previously seen'). Correctness plus clean, tight, edge-case-correct code is what is graded. An August 2026 sitting reports the pool is drifting: 2 of 3 problems were still from the known canon with trivial modifications, but the third was a new tree construction / manipulation problem solved with DFS ('merge trees') - independently reported as the hardest problem on the OA and not yet in our bank. Two candidates flag it, so budget time for it: practice building trees from serialized input, merging two trees node-by-node, and DFS-based manipulation; conceptually it is not hard, but it is the time sink.
Fancy NumberCount base-4 numbers using only digits 0 and 1 that are less than n, faster than O(n) - binary<->base-4 bijection or digit DP.Reversi / OthelloApply a sequence of stone placements; flip bracketed opponent runs in all 8 directions; return final black/white counts.Ghost Word Game (Prefix Game)Two players append letters keeping the string a valid dictionary prefix; whoever is forced to complete a word loses - trie + game theory.2048 SimulatorSimulate 2048 on a 4x4 grid: slide-and-merge per move (rotate so every move is 'left'), then place the added piece.see all 6 in the pool →Classic LeetCode-style coding, often a CodeSignal 'General' resume-screen auto-send at medium difficulty. Early intern OAs (2019-2020) were C++-only and ran up to 4 hours.
Add BinaryAdd two binary strings and return the binary sum (LeetCode 67) - HRT high-frequency.Max Chunks To Make Sorted IIMax number of chunks so sorting each and concatenating sorts the array (LeetCode 768) - prefix-max vs suffix-min.Maximize by Changing One DigitDigits are 6 or 9; flip at most one to maximize (LeetCode 1323) - flip the first 6.Longest String With No Three Equal in a RowGiven counts of a, b, c, build the longest string with no 3 identical consecutive chars - greedy max-heap.see all 10 in the pool →A short, C++-only screen for the Quant Analyst role: 30 minutes, two low-level problems testing idiomatic modern C++ - parsing a packed binary buffer and writing a container-rendering template. Both correctness and clean, type-safe C++ are graded. (Quant Researcher candidates take the Algo Developer assessment above.)
Parse a Length-Prefixed Binary BufferRead a char, a 4-byte int, and a length-prefixed string from a byte buffer, advancing the pointer past each.Templated Container RendererOne C++ template that renders any map of int/string keys and values, substituting UNKNOWN / UNSPECIFIED for empty entries.The first stage is on us — you're seeing it in full. Unlock every later round, the must-do problems, and stage-by-stage prep across all 56 firms with QuantVault Pro.
Looking for other firms?
Every firm has a curated interview-questions playlist — a ready-to-drill set of problems matched to how that firm interviews, each with a full worked solution.
Practice every firm's OA: timed replicas, free game replicas and guides in one place →
Hudson River Trading round-by-round guides
Hudson River Trading interview guide: the firm, culture, roles and pay →
Stage guides for every firm: superdays · behavioral questions · market-making games
Hudson River Trading interview — FAQ
What is the Hudson River Trading interview process?
HRT is famous for some of the hardest mental-math and probability questions in the industry. Coding screens are short and exact; onsites are conversational but mathematically demanding. Expect to derive results live on a whiteboard, often without a calculator. The loop runs 4 stages: Online Assessment, Probability & Brainteaser Phone Screen, Programming Phone Screen, Onsite (Final Round).
How many rounds does Hudson River Trading have?
4 stages in total, starting with the Online Assessment and ending with the Onsite (Final Round).
How do I prepare for the Hudson River Trading interview?
Work the stage notes above, then drill the Hudson River Trading interview-questions set and the Hudson River Trading online-assessment practice — each problem has a full worked solution.