Pergunta de entrevista da empresa Whatnot

It is a leetcode question that involves graph building. The problem is about medium difficulty. What made it very hard was that they wanted to make the problem sound practical by giving you a "real-world-like" scenario where you must figure out the leetcode requirement yourself. The interviewer doesn't provide much additional information/confirmation after I summarized my understanding, so it took me a while to realize that I had gone in the wrong direction.