Not to take anything away from the guy - he's clearly gifted and hard working - but it's really not. As anyone that's ever seriously prepared for interviews (ie >200 problems on LC) will tell you there's just not that many distinct problem types and so you just send up solving variations of the same 30 over and over. No doubt sometimes the subtle difference is killer (and Gena has blog posts about some of those) but generally solving is just pattern matching.
