Implement a function to traverse cell dependencies in an Excel-like spreadsheet and detect circular references between cells.

"I got in through a referral, and the process was a recruiter screen, one LeetCode-style technical screen, then an onsite that included a take-home plus three 1-hour rounds. For a startup, it felt weirdly mature and standardized, more like big tech: everyone I met was in the agent engineering org, the recruiter was polished, and they were even fine with me pushing the coding screen out by over a month. The phone screen was a pretty standard cycle-detection problem dressed up as an Excel question, and then the take-home was much more job-relevant because I had to build a small customer support agent and think about prioritization, metrics, and observability. Most of the loop felt friendly and professional, but the big gotcha was a TypeScript and React debugging round that they framed as conceptual even though I think you really do need to know that stack to pass it. I didn't get the offer, and honestly I think that debugging round was the reason because the rest of the process felt solid."