I had an interview with a company working in the ML space. There is a semi-difficult problem that their particular industry needs a solution for so I spent a couple hours in the hotel the night before writing up a solution for it.

I was doing an interview with their head of ML and brought this subject up in general without mentioning that I had already solved it. His immediate response was: "that's impossible." And it was totally concrete, not some sort of challenge. He had no interest in discussing the topic at all.

Those kinds of people are out there. Best to detect them early and move on.