Here are my solutions to Advent of Code 2015. I solved Days 1, 2, 3, and 5 back in 2015 using Ruby. Interesting to see how I thought back then!
In 2020, just for fun, I did Day 4 using Go (I now know what an MD5 hash is!).
In 2019, 2018, and 2017 I used Rust in my Advent of Code attempts.