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This repo contains solutions for the advent of code (http://adventofcode.com) written in Erlang.

Code files contain solutions for the problems in various days. If you would like to know more about a particular solution, the more complicated ones have short explanation in the module comments.

To run the examples simply use rebar to build it. Do not forget to fetch dependencies. One of the examples (day12) utilised the jsx library to manipulate JSONs.

rebar get-deps
rebar compile

Some examples use excessive amounts of processes, just because it is more fun that way. Erlang VM has a limit on the max process count, that defaults to around 200000. You may want to start your Erlang VM with the +P flag:

erl +P 2000000

About 2 million process limit should do it, although it never really goes much about one million. :)

• Day 6 - The VM has a limit on how many processes can be spawned. This is configurable, but must be remembered.
• Day 6 - Large ETS tables can be quite slow when performing selects. This may imply gproc may struggle when there's a LOT of processes running, although normally you probably wouldn't store ALL PIDs in one place.
• Day 20 - Every math problem can be brute-forced with enough processes!
• Day 20 - The catch expression seems to work in a strange way and not very well when there's a LOT of processes. Perhaps more investigation is required.
• Many days - Erlang and string operations to not add up nicely. But we all knew that. Same applies to large arrays.