Do you need C++ for quant interviews?

Only for some engineering seats. In the 2027 postings of 18 quant firms read on 21 October 2026, no quant researcher or trader posting required C++, and 16 of them named Python. C++ was the only acceptable language on three engineering postings, each with C++ in the title: Akuna's C++ internship, Jump Trading's APAC C++ internship and Tower Research's Montreal C++ new-grad role.

Can I use Python in an HRT coding interview?

Yes. HRT's engineering blog (October 2025) says candidates choose between C++, Python, or TypeScript/Python for fullstack roles, and that the quality bar is the same in each. It also says candidates who interview in C++ are expected to have a fair bit of low-level knowledge. HRT's Summer 2027 software engineering internship is titled 'C++ or Python'.

Do I need to know OCaml to interview at Jane Street?

No. Jane Street's interviewing page says you can interview in whichever language you know best and strongly encourages you not to try OCaml for the first time in an interview. Its 2027 software engineer posting says it does not expect a background in functional programming, OCaml or Python.

Which quant firms require C++ for software engineering roles?

Among postings read on 21 October 2026, Akuna's C++ software engineer internship asks for modern C++ (C++20 or later, C++23 preferred), Jump Trading's APAC C++ internship asks for proficiency in C++, and Tower Research's Montreal new-grad C++ developer role asks for excellent C++. Most other engineering postings, including HRT, Optiver, DRW, Two Sigma and Citadel, list C++ alongside Python or Java.

Can you use AI tools in quant coding assessments?

Assume not. HRT's 2027 postings say AI use in interviews or assessments is strictly prohibited unless agreed, Two Sigma says perceived AI use could disqualify you, IMC's interview code of conduct bans AI and code-generation tools, and Akuna says AI use will result in disqualification.

C++ vs Python in Quant Coding Interviews (2026): Firm by Firm

Choose the seat first and the language second. In the Summer 2027 and 2027 new-grad postings of 18 quant firms we read on 21 October 2026, no researcher or trader posting required C++, and C++ was the only accepted language on just three engineering postings, each with "C++" in its title. Everywhere else, C++ sits next to Python or Java, and most firms that publish their interview rules let you code in the language you know best.

The mistake most applicants make is treating C++ as a signal of seriousness. Hudson River Trading's engineering blog says that if you interview in C++ at HRT, "you are expected to have a fair bit of low-level knowledge". Picking C++ for a round buys you harder follow-up questions, not extra credit.

Firm by firm: what the 2027 postings say

Read from each firm's careers site or Greenhouse feed on 21 October 2026 unless marked otherwise.

Firm	Engineering posting asks for	Research or trading posting asks for	Interview language rule
Jane Street	SWE: no OCaml, functional or Python background expected	QT intern: no particular language; QR intern: comfortable with Python	"Whichever language you know best"; don't try OCaml for the first time
Hudson River Trading	SWE intern "(C++ or Python)": Python, C or C++	Algo Dev intern: Python a must, C++ desired for low latency	C++, Python, or TypeScript/Python for fullstack (HRT blog, Oct 2025)
Jump Trading	Chicago SWE intern: C++ or Python on Linux; APAC C++ intern: proficient in C++	QT intern: "programming experience"	Not published
Optiver	Chicago SWE intern: C++, Python or Java	Quant intern: Python or another language	Sydney 2027 grad: C++, Java or Python for the technical assessment
IMC	Chicago SWE intern: Java or C++ preferred	QT intern: Python, Matlab or R a plus	Application form asks which of Java, C++ and Python you know
Susquehanna (SIG)	Trading System Engineering intern: C++, C, Rust, C# or Java, plus some Python	Master's QR intern: Python; C++ a plus	Not published
Akuna Capital	C++ intern: C++20 or later, C++23 preferred	QR intern: intermediate Python	Not published
DRW	Software Developer intern: C++, Python or Java	Quant Trading Analyst intern: Python	Timed at-home challenge first
Tower Research	QD intern: C++ and Python preferred; Montreal new grad: C++	QT/QR intern: C++ and Python preferred	Not published
Five Rings	SWE intern: Python required, C/C++ preferred	QT intern: no language listed	Not published
Citadel*	SWE new grad: C++, Python preferred	QR intern: Python, R or C++	Not verifiable
Two Sigma	SWE campus: Java, C, C++, Python and others	QR intern: one of C, C++, Java or Python	C, C++, Java or Python in a shared codepair
D. E. Shaw	SD intern: Python, Java or C/C++	Quant Analyst intern: Python preferred	Fluency in a specific language not required
Millennium	QD intern: Python, C++ or Java	QR intern: Python; C++ a plus	Not published
Point72 / Cubist	Point72 QD intern: production-quality Python	Cubist QR PhD intern: Python or C/C++	Not published
G-Research	SWE intern: C#, Java or C++	QR intern: ideally Python or C#	Online test first
Squarepoint	Graduate QD: Python, C++ or kdb+/q	QR intern: e.g. C++, Java, Python	Not published
Marshall Wace	Technology early careers: Codility test	QR intern (London): Python, R or MATLAB	Some Codility questions use a set language

*citadel.com blocked automated access, so the Citadel row comes from Built In's copies of its postings.

Count the research column: 16 of 18 postings name Python, the other two name no language, and none requires C++ on its own. In the engineering column, C++ is non-negotiable only on Akuna's C++ internship, Jump's APAC C++ internship (the posting says "C++ is our primary language and it touches everything we do") and Tower's Montreal C++ new-grad role.

Where the language actually gets tested

The algorithm round rarely decides the language question. The rounds after it do.

Stage	Typical format	Language rule	Extra for C++ candidates
Online assessment	HackerRank, Codility or the firm's own platform	Usually your choice	Akuna's reportedly opens with ten C++17/C++20 multiple-choice questions (Tradermath)
Phone screen	30-60 minutes in a shared editor	Your choice at HRT, Two Sigma and Jane Street	Usually nothing extra
Low-level or systems round	Discussion plus implementation	Follows the track you applied to	Memory, concurrency, rebuilding standard-library classes
Research coding	Data exercise or modelling task	Python with numpy and pandas	Rarely
Final round	Increasingly in person	Same as earlier rounds	Design and debugging

Online assessment. Tradermath's quant developer guide (updated 17 October 2026) says HackerRank runs the assessment at nearly half of the top firms. Optiver's London internship posting asks you to take its test within seven days, and Optiver will not let you reapply for eight months after an assessment. Marshall Wace's technology guide warns that some Codility questions "may require you to use a specific language you may not be familiar with", and that this is by design.

Phone screen. A February 2025 Blind poster described HRT's 30-minute screen as a CoderPad round in Java, C++ or Python, separate from the low-level round where you explain C++ and compilers. Two Sigma's interview page describes three 60-minute technical interviews in C, C++, Java or Python.

Low-level round. Optiver's interview tips (March 2025) say its rounds are not standard LeetCode puzzles and tell candidates to revise computer architecture, networking, concurrency and memory management. IMC's European technology prep guide lists memory, computer architecture and concurrency, suggests A Tour of C++ or Effective Java, and says you are not at a disadvantage if you skip them. A Jump-tagged Blind reply from June 2025 listed RAII, virtual dispatch, template metaprogramming, move semantics and concurrency, and warned that candidates may be asked to implement `shared_ptr` or `vector`.

Research coding. Tradermath's researcher guide (September 2026) puts the bar at solid Python with numpy and pandas, and says systematic funds are more likely to include a small data task, such as implementing linear regression efficiently in numpy.

Final round. Jane Street's software engineering prep page says the technical interview runs over Zoom and the final rounds are in person at one of its offices, in "a real programming language", not pseudocode. Elsewhere it varies: in a September 2026 Blind thread, a Citadel-tagged reply said SWE onsites can be online and two HRT-tagged users contradicted each other. Ask your recruiter.

How to choose your interview language

The posting has C++ in its title: use C++ and prepare for the low-level round.
The posting says "C++ or Python": pick the one you can defend under follow-up questions. HRT says its bar is the same in both, but its Trading Tech teams work roughly 70% in C++ and its R&D teams roughly 70% in Python, so your choice also points you at a team.
Research or trading seat: Python. Every research posting in the table accepts it.
Jane Street: your strongest language. Its interviewing page says most engineers it hires arrive without OCaml or functional-programming experience.
Unsure: ask the recruiter what the team writes. In a September 2025 Blind thread about a Citadel Securities C++ interview, a Citadel-tagged reply said interviewers would be "really confused" by Python, while another reply said it depends on the team and interviewer.

For scale, Python is far more common in general: 58.0% of the 14,099 developers who answered the language question in Stack Overflow's 2026 survey (published 6 October 2026) used it, against 24.3% for C++ and 1.2% for OCaml. The firms that hire for C++ are investing in it anyway. Susquehanna was a platinum sponsor of CppCon 2026 and brought on Bjarne Stroustrup, the creator of C++, as a technical fellow (CppCon, August 2026).

What gets people rejected

1. Choosing C++ to look serious. You inherit the low-level follow-ups HRT describes. If you cannot explain move semantics or the cost of a virtual call, Python is the safer choice where it is allowed.

2. Python in a C++-labelled interview. See the Citadel Securities thread above. If the job title says C++, so does the interview.

3. AI tools in the assessment. HRT's postings say AI use in interviews or assessments "is strictly prohibited" unless agreed, Two Sigma says perceived use could disqualify you, IMC's code of conduct bans AI and code-generation tools, and Akuna says AI use "will result in disqualification". The jobs themselves are different: Jump's Chicago SWE intern posting lists experience with AI tools such as Claude Code as a plus, and Millennium's QR intern posting asks for the ability to apply AI tools in quantitative workflows.

4. Spending your one application on the wrong track. Applying to Akuna's C++ internship means you will not be considered for its other quant or tech roles this season. HRT's internship postings say "We do not allow multiple applications". Optiver's cool-off is eight months.

5. Cramming OCaml for Jane Street. The firm tells you not to.

6. Trusting prep-site language lists over the invite. Tradermath says Optiver's coding assessment does not accept Python; Optiver's own Sydney 2027 graduate posting says C++, Java or Python experience is required for its technical assessment. Read your invite.

For international students

Jump's Chicago SWE intern posting says it accepts students eligible for CPT or OPT and sponsors work visas for full-time positions. Marshall Wace's London QR internship starts with a test at a local centre that it says it cannot run virtually, and Jane Street's in-person finals mean booking travel early if you study far from an office. On language, IMC's prep guide says the goal is to structure the problem, weigh trade-offs and communicate, not to write flawless code on the first try, so practise explaining your code out loud in English.

A 4-week plan

Week 1: Pick a lane per application. Copy each target posting's language line and choose one interview language per firm. Make sure your CV's skills line leads with the same language, and track open roles on the New Grad 2027 tracker.
Week 2: Timed algorithms in that language. One medium and one hard problem a day in a 30-minute shared editor, without autocomplete or AI. A Google-tagged Blind reply reported a segment-tree DP problem at HRT, so do not stop at mediums.
Week 3, C++ lane: implement `vector`, `shared_ptr` and a single-producer ring buffer from scratch, and explain move semantics, virtual dispatch, cache lines and memory ordering out loud. Week 3, Python lane: numpy and pandas drills, linear regression from scratch, and one research notebook you can walk through cleanly.
Week 4: Mock the real rounds. Applr's Optiver software engineer mock asks lock-free, cache and memory-model follow-ups; the Jane Street software engineer mock covers language-agnostic coding; Python researchers can use the HRT quantitative researcher mock. Still choosing a seat? Our QT vs QR vs QD guide compares them.

C++ vs Python in Quant Coding Interviews (2026): Firm by Firm

Firm by firm: what the 2027 postings say

Where the language actually gets tested

How to choose your interview language

What gets people rejected

For international students

A 4-week plan

Sources

Frequently asked questions

Practice for top companies

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