These are not guaranteed to be complete. I do them when I have time.
Both 2021's and 2022's solutions are in ngn/k, grouped in a single file soln.k, in which solution functions are listed as sXY, X being the day number, Y being part 1 (a) or part 2 (b), for example s5b is the part 2 to day 5.
2023's solutions are in noulith (this is forked, but my changes add some useful features which may or may not get used). Solutions are as dXY, X being the day number and Y being part 1 (a) or part 2 (b), for example s5b is the part 2 to day 5. Same goes for input/test files just without the d. There's run.noul that makes it a little easier to run/test stuff on given inputs.