I have a coworker at Unity who's been wiping the floor with all of us with his compact, efficient #adventofcode solutions. What makes it especially galling is that he's doing it all on a 16 MHz 386SX, using Borland Turbo C++ 3.0. Even his write-up looks like a Wayback Machine snapshot of an early-90s Geocities homepage: http://clb.confined.space/aoc2022/

Go, be impressed!
(EDIT: the link was broken, but it's back now with further updates)