Advent of Code 2020

January 10, 2021


I finished the Advent of Code for 2020, and this time pushed myself past the holiday indulgences to actually complete all 50 challenges!

I pushed myself to use Elixir for everything this year, and barring a few small instances where being able to mutate a value would have saved me a lot of headaches (specifically this evil creation) it was a pretty awesome experience. Aside from the usual 2D grid geometry problems, there were a lot of new things in there and I discovered some nice things on the way.

Here's some unsorted notes and discoveries I made during the whole process.


  • Elixir's pattern matching is really nice for interpreting VM instructions
    • Just pattern match the op code, extract the params and do the operation!
  • Conway's game of life can be extended to higher dimensions (hypercubes of life haha)
    • Simply keep track of the live nodes, and create a function to find the neighbors of each node
    • The number of times a certain neighbor is duplicated in the output is the number of live neighbors it has
    • By changing the neighbor function to work on 2D, 3D or 4D coordinates, you get the behavior of the system in a higher dimension!
  • Day 20 was by far the most involving
    • To even get to validate the test cases took a lot of effort
    • A lot of image convolution
  • Elixir / Erlang map keys are ordered by default up to 32 entries
  • Regex lookahead is a thing
    • I've somehow never needed to find overlapping matches in a pattern space before
    • A deep sense of fear sets within me..

Checkout the code in my GitHub Repo


Nifty tech tag lists fromĀ Wouter Beeftink