Given an organizational hierarchy, how would you model it so I can quickly find a person's direct reports and everyone under their department?

"I applied directly on the website with no referral and went through a pretty Google-like process. The loop was a basic recruiter chat, then a surprisingly hard LeetCode-style coding screen, then a final loop with another coding round, an ML coding round, an ML system design round, and two behavioral rounds. What really stood out was that the coding bar felt basically software-engineer level, not a watered-down MLE bar, and then on top of that they still expected solid ML depth. The strangest round for me was the final coding interview because it was more practical and diagram-based than I expected, while the behavioral rounds went deeper into the technical details of my projects than most companies do. Do not under-prepare on DSA just because the title says machine learning."