OpenAI Machine Learning Engineer Interview Experience — A Simulation-Style Infectious Disease Question

I interviewed onsite for a completely new question I had never seen before -- five parts in total, and I only managed to finish three, so I definitely failed this round.

The prompt was described as "simulation style." Beforehand, people on the forum said it would probably be GPU-related, so that is what I prepared for, but it turned out to be about infectious disease instead. Posting this so other people can prepare.

The question: there is an n x m grid where the people in each cell might be infected. If a healthy person has N infected neighbors, they also become infected. The question asks how long it takes until everyone ends up infected.

There were five sub-questions total, each one more complex than the last, with a 60 minute time limit.