SIG (Susquehanna) Interview Questions — Page 2

SIG (Susquehanna)·Software Engineer·Technical Phone Screen

Apr 2026

SIG software engineer interview with a classic systems design problem dressed up as a coding question. The movie theatre seat booking problem sounds almost trivial until you're actually in it and realize how many design decisions stack up fast.

Design and implement a movie theatre seat booking system that supports booking a group of adjacent seats, cancelling bookings, and optionally handling a middle aisle that splits each row into two segments. Discuss your data structures, time complexity, and how you'd handle concurrency at scale.

“I started with a naive per-row array scan and the interviewer immediately pushed on what happens with a 10,000-seat venue under heavy load.”

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SIG (Susquehanna)·Data Scientist·Technical Phone Screen

Apr 2026

Probability question from a SIG data scientist interview. Classic Bayesian setup, nothing too wild, but the arithmetic is easy to fumble under pressure.

Factory A produces 40% red and 60% black widgets; Factory B produces 80% red and 20% black widgets. A factory is chosen at random, then two widgets are drawn from it. Given that both widgets are black, what is the probability they came from Factory A?

“This is straight Bayes.”

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SIG (Susquehanna)·Software Engineer·Technical Phone Screen

Apr 2026

SIG quant researcher interview, got hit with a logic puzzle about cats and truth-telling rules. Pretty classic SIG flavor, the kind of thing where you either see the structure fast or you're just spinning.

Asta, Bronya, and Clara each own a different number of cats. The rule is: if you're talking to someone with fewer cats than you, you tell the truth; if they have more, you lie. Given their conversation, figure out how many cats Clara has.

“This type of puzzle wrecked me the first time I saw something like it.”

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SIG (Susquehanna)·Software Engineer·Take-home Assignment

Apr 2026

SIG quant researcher take-home: three days to analyze a trading ledger with seven traders and come up with a strategy that actually makes money out-of-sample. Pretty open-ended, which I liked and also found stressful.

Given a trading ledger for a single asset traded by multiple traders, propose a strategy that maximizes return. Include exploratory analysis, signal identification from trader behavior, a clearly defined strategy rule, an out-of-sample backtest with return/Sharpe/drawdown metrics, and a written discussion of assumptions and risks.

“Three days sounds like a lot until you realize how much they actually want.”

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SIG (Susquehanna)·Software Engineer·Onsite - Coding / Algorithms

May 2026

Second part of a virtual onsite at Sig for a software engineer role. The interviewer was relaxed but the follow-ups on the ticker trie problem had some teeth. Worth knowing they leave you alone for 30 minutes to code, which is a different format than most places.

Design and implement a trie data structure for storing and querying stock tickers, then handle follow-up variations on the core problem.

“The base trie part felt manageable but the follow-ups are where things got interesting.”

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SIG (Susquehanna)·Software Engineer·Technical Phone Screen

May 2026

SIG quant engineer interview, got hit with a stats/probability design question that was more involved than I expected. One round, fairly technical, felt like they wanted to see how you structure a full hypothesis testing argument from scratch.

You have n players in a game and you've recorded win/loss results over many rounds. How do you test whether the game is purely luck versus skill-driven? Walk through building a chi-square goodness-of-fit test, including the null hypothesis, the test statistic, degrees of freedom, and any limitations you'd flag.

“This took me a second to land on the right framing.”

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SIG (Susquehanna)·Data Scientist·Technical Phone Screen

May 2026

SIG probability/gambling theory question for a Data Scientist role. Classic quant-style problem that feels more like a trading interview than a data science one, but I guess that tracks for SIG.

You start with 3 tokens and want to reach 5 before going broke. Each turn you bet as many tokens as you can without overshooting 5, and each bet wins independently with probability 3/5. What's the probability you reach 5 tokens?

“This one took me a minute to set up properly.”

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SIG (Susquehanna)·Software Engineer·Technical Phone Screen

May 2026

Sig SWE interview that leaned heavily on tree fundamentals, with a small coding component tacked on. More conceptual than I expected but the BST implementation part was pretty standard once I got my bearings.

Walk me through the main types of trees as a data structure family and give a real-world use case for each.
Give me a precise definition of the binary search tree ordering invariant, not just 'left is smaller than right'.
Implement an in-order traversal of a BST that prints keys in sorted order, and also implement a search that returns whether a key exists. Discuss time and space complexity for both, and how tree shape affects them.
How do AVL trees and red-black trees maintain O(log n) operations, and what are the tradeoffs between them?
Why do databases and filesystems prefer B-trees or B+ trees over binary search trees for on-disk indexes?
How would you verify in O(n) time that a binary tree is a valid BST, and what's the subtle bug in just checking each node against its immediate parent?
When is a hash table a better choice than a BST, and when does the BST's ordering property make it irreplaceable?

“I kind of rambled at first, listing types in no particular order.”

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SIG (Susquehanna)·Software Engineer·Technical Phone Screen

May 2026

SIG quant researcher interview with a probability puzzle that looks clean on the surface but has a sneaky conditional piece that'll trip you up if you're not careful.

Three cats each have different win probabilities in a jumping contest (1/2, 1/3, and 1/6 for most, middle, and least athletic respectively). You randomly pick one cat to root for, but it loses. What's the probability your cat was the most athletic one?

“The setup is simple enough but the conditioning is what gets you.”

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SIG (Susquehanna)·Software Engineer·Technical Phone Screen

May 2026

SIG quant researcher interview, got hit with a classic logic puzzle. Pretty clean problem but the reasoning has to be airtight or you'll talk yourself in circles.

There are two people, A and B, each either a knight (always truthful) or a knave (always lying). B makes two statements: first, that A and B are the same type; second, that A always lies. What type is each person?

“I actually enjoy these puzzles but I still managed to second-guess myself halfway through.”

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