Detect circular dependencies between fields in the CSV data.

"The biggest thing that stood out was how little it felt like normal LeetCode. The first technical was a long CSV parsing and validation problem with multiple parts, and the real skill was extracting the actual problem from all the words and then implementing simple logic quickly. The next round was an integration repo round where I had to read unfamiliar code, figure out which APIs or endpoints to call, and wire data into an endpoint and CLI output. That one felt more like design than coding to me. Overall I liked the style more than typical coding screens because it was straightforward, but you do need to read fast, type fast enough, and stay calm with ambiguous real-world setup."