These are my solutions for Advent of Code 2020. The only thing being optimized for here is "speed to find the solution", which is roughly ("time spent writing code" + "time spent running code" + "time spent debugging code"). As such, many solutions contain copy-pasting, poorly-thought-out method signatures and variable names that I didn't take time to change, and unoptimized logic which would be problematic if any of these programs had to run more than exactly once.
Many solutions contain the same copy-pasted helper functions at the top, which I accumulated over the course of the month. I copy-paste them into each solution rather than creating a separate library because 1. I don't want to make a change and break previous solutions, and 2. I didn't want to deal with dependency management in case I needed to switch to a different .NET version.