Looking at the skills section on his webpage: http://www.cirosantilli.com/skills/ This seems like the most honest self-assessment I have seen of one's skills.
I interviewed with Snapchat a few years ago and was asked to write a Sudoku solver. Some context: I had never played Sudoku in my life, lol. I came up with a naive (unoptimized, unrefined) solution and didn't get past their third round.