Recently experienced a Jane Street I have to say that this company really lives up to its name. The interviews are not traditional coding interviews, but a collection of probability, expectation, game theory, and auction modeling. The whole process is like doing a high-intensity intellectual game. I'd like to share my questions and thoughts for those who are preparing for quant/trading firms.
Jane Street Interview Process
| classifier for laps, turns, rounds | Field of investigation | Examples of questions | Note |
|---|---|---|---|
| Round 1 Probability + Basic questions | Probability theory, expectations, combinatorial counting | - Calculation of wall-scrubbing efficiency - Coin toss expectations - Dice and payoff - Bear catching fish probability | Basic Math Intuition + Rapid Reasoning |
| Round 2 Game Theory & Strategy Questions | Nash Equilibrium, rational man game, information asymmetry | - $100 box game - Fixed strategy with multiple rounds of opponents - Information value calculation - Sequence of coins game | Strategic Analysis + Modeling Capabilities |
| Round 3 Auction / Market Simulation | Bidding mechanisms, market equilibrium, first/last hand analysis | - Double Dice Auction - EV (first hand) vs EV (second hand) | Market Intuition + Gaming Strategy |
Jane Street Interview Questions
1 wheel
- A takes 1 hour to paint the wall, B takes 2 hours to paint the wall, how long does it take A and B to paint the wall together?
- Toss 4 coins and the probability of at least two heads.
- Toss 4 coins, one heads is worth $1. After observing the first result, you can either accept the result or toss all the coins a second time. After observing the first result, you can either accept the result or toss all the coins a second time, after the second time you must accept your payoff. ask what your strategy was and how much the expected payoff was.
- One die 1 - 6, one die 1 - 10, guess the sum of the two dice, if you guess correctly you get the payoff corresponding to the sum, and guess how much to get the maximum expected payoff.
4.1. Follow - up: What if we say a die 1 - 20 and a die 1 - 30? - 4 coins flipped two at a time, final expectation (3.5)
- A bear is satiated by eating 3 fish and the probability of catching each fish is 1/2, ask the probability that the fifth fish survives (11/32)
2 rounds
- A box has $100 in it, and your opponent is the rational man. You and your opponent both write numbers on a piece of paper, and if the sum of the numbers 100, you get nothing. Ask what your optimal strategy is.
- Now don't assume your opponent is a rational person. Play the same game 1000 times. The first time, your opponent says he's going to play 80. What do you do?
2.1. follow - up: (This follow - up is because I asked if I should bid 20.) If the game is played ten times and he bids 80 each time, what would be your trade-off? - Assume again that your opponent is the rational man and will play the game only once, but now there are 10 boxes. 5 boxes contain $40 and 5 boxes contain $50, and then you both have to write 10 numbers for each of the 10 boxes, with the payoff for each box determined in the same way as in the first question. What is your optimal strategy?
3 - 1 Suppose you have purchased some information about how much money is in each of all the boxes. What is your optimal strategy when your rival does not know this information and does not know that you know it? What is the most you would be willing to bid for this information? (50)
3 - 2 20 or 100 per box? (0) - Always flip a coin (heads probability 2/3, tails 1/3), you say a binary sequence first (HH, HT, etc.) and your opponent says it after you. You say a binary sequence (HH, HT, etc.) first and your opponent says it after you. The first person to throw the sequence wins, win $10, lose - $10, will you play? (No. Maximum win rate 4/9)
3 rounds
There is an auction with two even 1 - 6 dice, and the sum of the numbers on both dice after the throw is the value of the contract. You and another person take turns bidding, with the order of precedence randomized. Only integers can be bid. You can see the number of the first die, and your opponent can see the number of the second die.
Optimal strategy: the first person bids 2, then everyone takes turns bidding up + 1. The upper limit on everyone's bids is that if you see a number X, then you can only bid up to 2X, otherwise you will lose money.
EV of going first than second = 5/12, the key to the calculation is to understand that according to the strategy above you can only win if your number is bigger than your opponent.
VO hard? There are people who can help you steady the pace
Jane Street's VO interviews are really testing! The pace was fast and furious, and it was easy to get sidetracked by the follow-up questions if you weren't careful. Good thing I have Programhelp The assistance of the seniors, the whole process to help me run through the logic, simulation of high-pressure scenarios, but also in the key points to remind me, really is a lifesaver ~ If you are also going to face the VO, highly recommended to find them to practice!
