Susquehanna 2026 OA usually uses CodeSignal or HackerRank, which varies slightly for different positions:
- SDE/Software Engineer: Mainly Coding (2-4 questions), partial to engineering implementation and OOP.
- Quant / Trading Intern: Heavy probability, brain teasers, quick mental arithmetic + a little coding.
- The overall duration ranges from 60 to 120 minutes, and some include logic games.
Let’s share a Susquehanna 2026 OA real question type + speed-passing ideas (based on recent candidate feedback).
1. Two trips
Question: I took two trips last year, one of which was an international trip in December. What is the probability that both trips are international trips?
Problem-solving ideas:
This is a classic conditional probability problem. Let event A be “both trips are international trips” and event B be “one of the trips is an international trip in December”. We need to solve P(A|B)=P(A∩B)/P(B).
First, assume that the two trips are independent of each other, let I represent the international trip and D represent the domestic trip. All possible outcomes of the two trips are II, ID, DI, DD, and the probability of each outcome is 1/4 (assuming equal possibilities).
- Event A (both international trips): The corresponding result is II, P(A)=1/4.
- Event B (an international trip in December): The situation is more complicated. Assuming that the travel months are random, the probability of a single trip being in December is 1/12, and the probability of being an international trip is 1/2.
We can first simplify the problem: given that at least one of the two trips is an international trip, find the probability that both trips are international trips. At this time, the sample space is {II, ID, DI}, the favorable outcome is II, and the probability is 1/3.
The limit of "December" in the question is most likely an interference item, so there is no need to overthink it.
More rigorous derivation: Suppose T1 and T2 are two trips, P(T1=I)=P(T2=I)=1/2, the result is still II, ID, DI, DD. It is known that at least one trip was an international trip. After excluding DD, the remaining possible results are II, ID, and DI. So, the probability of both trips being international trips is 1/3.
2. Roll the dice alternately
Question: Two fair dice A and B are rolled alternately (A first and then B), and the game ends when A rolls 6. Find the probability that the game ends when A rolls the die.
Problem-solving ideas:
This is a confusing logic question. The game only ends when A rolls a 6, so the game must end at A's dice phase with probability 1.
3. Expected number of dice rolls
Question: Based on the previous question, find the expected total number of dice rolls to complete the game.
Problem-solving ideas:
The game ends when A rolls a 6, and A's dice rolls are rounds 1, 3, 5... Let E be the total expected number of dice rolls, the probability of a single A rolling a 6 is 1/6, and the probability of not rolling a 6 is 5/6 (B's dice rolling result does not affect the ending condition).
- The game ends on round 1: A rolls 6, probability (1/6)×1;
- The game ends in the 3rd round: A does not roll, B rolls any, A rolls 6, probability (5/6)×1×(1/6);
- The game ends on the 5th round: A has not, B has any, A has not, B has any, and A rolls 6, with probability (5/6)2×(1/6).
This distribution is not a simple geometric distribution, and it is necessary to analyze A's dice rolling rounds: A's dice rolling times follow a geometric distribution (success probability 1/6), and the expected number of times is E[K]=1/p=6. Each round A rolls the dice (except for the last round) corresponds to B's roll once. If A rolls K rounds in total, the total number of rounds is K+(K−1)=2K−1.
So, the total expected number of times: E[2K−1]=2×E[K]−1=2×6−1=11.
4. Waiting time paradox
Question: The departure intervals of the two bus routes A and B obey the uniform distribution U(0,10) and U(0,20) respectively. If passengers arrive randomly, find the average waiting time.
Problem-solving ideas:
This is the classic "testing paradox" problem. If the random variable of the departure interval is X (mean E[X]), then the average waiting time when passengers arrive randomly is not E[X]/2, but E[X2]/(2×E[X]).
Route A (U(0,10))
- Mean: E[A]=(0+10)/2=5;
- Variance: Var(A)=(10−0)2/12=100/12=25/3;
- Second moment: E[A2]=Var(A)+(E[A])2=25/3+25=100/3;
- Average waiting time for individual routes: (100/3)/(2×5)=10/3 minutes.
Route B (U(0,20))
- Mean: E[B]=(0+20)/2=10;
- Variance: Var(B)=(20−0)2/12=400/12=100/3;
- Second moment: E[B2]=Var(B)+(E[B])2=100/3+100=400/3;
- Average waiting time for individual routes: (400/3)/(2×10)=20/3 minutes.
SIG OA & experience sharing
After passing SIG OA, it usually goes to Technical Phone / Behavioral + Trading / System Design round. Quant also involves more games of chance and brain teasers.
If you are preparing for Susquehanna SIG 2026 SDE / Quant Intern / New Grad OA, please leave a message or communicate via private message:
- Want to see detailed Python/Java code for specific coding problems (DP gas station, OOP Order Book, etc.)?
- Need probability brain teasers and high-frequency questions + analysis?
- Want to know about SIG follow-up interview (Quant Round, System Design, Behavioral) experience?
- Programhelp has helped tens of thousands of students successfully pass OA from top quant companies including SIG, making it truly efficient and worry-free.
I wish everyone to pass the 2026 SIG OA smoothly and get your favorite offer as soon as possible! Stay calm, think quickly, and sprint~
