Advent of Code 2021

These are my Advent of Code 2021 solutions written in Scala 3, Haskell, Python and Rust.

Remarks

• Scala solutions are short and concise, be sure to check them out.
• The solutions are self contained, they can easily be executed as shown in the next section. This also makes them just a bit cluttered because the parsing and the part selection are inside the same file.
• Both parts of each problem are solved in the same file, this requires a bit of generalization to solve both parts with almost the same code, and makes the code longer than other solutions.
• These are not the shortest or fastest solutions, but they are readable and show the key ideas for solving each problem and how to translate them to each different language.
• The Python solutions are a bit clunky because these are the ones I code first.
• The solutions in Rust are not so good because this is the first time I use Rust for this kind of problems. It gets better day by day, but don't expect amazing code.

Running the solutions

The solutions are self-contained and should run easily using the appropriate interpreter/compiler for each language, keeping the following considerations in mind:

• Input is taken from standard input.
• Either 1 or 2 must be passed as arguments to choose which part to run.

Scala 3

For example, to run the Scala solution for the second part of the first day, you can use the following command:

cat day01/test01.txt | scala day01/Day01.scala 2

Haskell

The solutions were tested with GHC 9.0.1, but 8.x should work too. No other libraries apart from base, containers and mtl are used, they should be installed by default.

cat day01/test01.txt | runghc day01/Day01.hs 2

Python

The solutions were tested with python 3.9, but they should work using any version >=3.8. Only numpy is used apart from the standard library.

cat day01/test01.txt | python3 day01/Day01.py 2

Rust

To run a Rust solution you must compile it first and then run the resulting executable:

rustc day01/Day01.rs
cat day01/test01.txt | ./Day01 2