I used to have a stack of books with references notes on my desk. The internet came and I could search and even stack-overflow improved this. Doing a whiteboard riddle from rote knowledge is something I always fail. That particular solution I maybe used it once or twice in my 30 years as SWE. Why would I remember this. I do remember where I can find the solution for it.

The heart of the coding interview is to get signal on a candidates’ willingness to join the cult.