Jane Street Software Engineer Interview Experience — OA Then a Phone Screen With Palindrome and Dice-Game Brain Teasers

I submitted my resume and got the OA email the next day. The problem was one that's already floating around the forum: using Excel to calculate a haircut, plus general Excel formula usage. Same numbers as the version posted on the forum, nothing changed. My suggestion if you're filling in the spreadsheet and need to use data from the problem's own table: use a reference, not copy-paste. The problem itself wasn't hard, and it's a take-home, so it's beginner friendly.

I submitted the OA on a Saturday and got the phone interview invite the following Monday, along with a request to fill in my availability for the next two weeks. That left me one week to grind from zero — I went through the forum and Glassdoor's tdo questions, and did some CoachQuant too, but in the end I got asked stuff I'd never seen before.

First question was simple: How many 3 letter palindromes are there with 26-letter alphabet? What about 5 letter palindromes? Felt like it was testing mental math — the interviewer said no calculator, so I dutifully did long division by hand... In hindsight, it was a phone interview with no camera on, so who would've known if I'd used one.

Second question: You play a dice game with 2 other friends. Three players each take turn to roll the dice, if there's a tie, the tied players re-roll. The player with the largest number wins. Now both of your friends rolled a 4, what is your chance of winning the game?

I misread the question at first — I thought it meant that if there's a tie, the tied players reroll first, and then I roll after. I got stuck on that for a while and had to ask for a hint. The interviewer told me that's not how it works: I roll first, and if I roll higher than 4, I win outright.

Given that, it's (2/6 chance I win outright) + (1/6 chance all three of us reroll) × (1/3 chance I win after the reroll).

Looking back, I think I choked on this one mainly because I started writing without fully understanding the problem, and once I got stuck I panicked instead of working through it. If I'd nailed down the details up front instead of diving in, I probably wouldn't have gotten stuck that badly.

And of course they also asked the classic "why Jane Street."