I applied through a friend’s referral at the NYC office.

First was the phone interview, coding on a shared document. It was a tough graph question. I had some trouble and had to ask for a hint at one point, but eventually got the correct solution. I heard back a couple of days later that they were going to bring me on-site.

On-site was a week and a half later and included two coding interviews, lunch, then a behavioral interview with a coding component in the second half, and finally a systems design interview.

First coding interview: The first problem went very smoothly. It was a medium-level problem involving using a stack. I asked clarifying questions first. The second problem was a tree traversal problem. I just could not come up with the “intended” optimal solution. I ended up having to go with the “dumb” solution, which I believe still had the same order of time and space complexity anyway, but was a bit ugly.

Second coding interview: This interview had easy coding problems. I think maybe they were testing my communication and absolute code perfection over intelligent solutions here. The first problem was a personal finance problem to calculate tax owed given income and tax brackets. The second problem was to, given a blank NYT crossword puzzle, output where the “clues” would be (i.e., where does “1 across” start and how long is it, etc.).

Lunch was lunch.

Behavioral: I didn't prep too much, but I came across as authentic because of it. I don’t know if there’s really a good way to prep for this. Soft skills come with time. For one question, I literally said, “I don’t really find myself in those situations at work,” which was fine, I guess. The coding part of this interview was actually pretty rocky. I had to add two binary numbers (represented as strings, i.e., “10110”). I believe this was also just to test communication and thought process.

Systems design: The problem was to design a simple version of Instagram that allows users to see friends’ images in a feed and also go to friends’ accounts to get that person’s images. To prep, look at the material the recruiter will give you. They gave me a GitHub link with a bunch of practice systems design questions and example solutions. Just learn what “kind” of solution they are looking for, and that will get you halfway there. (They want boxes and arrows representing the different components and how they interact). I only prepped for systems design the night before and was fine. It didn’t even go that amazingly; I had a hard time figuring out how to get the latency down for refreshing the feed, which required what I considered significant help.

A week and a half later, I got an offer.

Given a mathematical expression in prefix (+ 5 (* 7 8) 9 10 33), evaluate it.

Given a binary tree, find the shortest path from a given node to the nearest leaf (not including itself). Possibly traverse backwards up the tree.

Given a list of tax brackets and their corresponding taxes, and an income, determine what that person owes in taxes.

Given a blank NYT crossword, output where all the clues would be.

Add two binary strings represented as strings.

Design a simplified Instagram.