Citadel Securities Software Engineer interview experience

The problem was explicitly about optimizing code: I had to improve an approach from O(n²) down to O(n). The prompt was based on the classic “best time to buy or sell stock” concept, which I’d already worked through on LeetCode before, so the core idea wasn’t totally new.

After I submitted the solution, I waited for feedback from the hiring team. The timeline they gave me was about a week, and that waiting period was honestly the longest part—once the coding was done, there wasn’t much I could do but wait.

I didn’t move forward to an offer from there, but the round itself felt like a solid