[hiAndrewQuinn]

No. In fact, I had never solved a Leetcode problem before. Every time a card came up that I had never attempted before, I simply flipped it over and typed in whatever answer was on the other side - but only the first time. Each other time I would try to remember as much of the solution as I could.

Eventually I got good enough that I started naturally thinking up solutions to entirely new problems without having to check the answer first, which is what one would expect if they were building new crystallized intelligence by practicing earlier problems.