These are my solutions to the Advent of Code. There is a top-level folder for each year. Inside each of those is a folder for each day. I write my solutions in Haskell, and I recommend that you use Stack to run them. For example:
$ cd 2017/1
$ stack 1.hs
1031
When working on solutions, I typically use ghcid to get fast feedback. For instance:
$ cd 2017/1
$ stack --resolver lts-13.0 exec --package ghcid -- \
ghcid --test main 1.hs
...
These solutions aren't meant to show best practices. They're quick and dirty. They are probably too clever for their own good.
You can find other solutions, both in Haskell and other languages, on this list: https://github.com/Bogdanp/awesome-advent-of-code.