It's results like this which put to rest the "myth" that "10x" programmers don't exist according to some people. In fact, it's been my experience that "100x" or even "1000x" programmers exist. (Fabrice Bellard is a prominent example of the latter.) For your given practice problem I'd probably spend more time reading it and writing the code than thinking, unless I'm asked to use something like an APL-family language in which case the majority of the time would be spent reading the problem description.

(Full-disclosure: mostly self-taught with several decades of experience.)