AoC 2022/1 - Caloric snacks


On with Advent of Code puzzle 1 from 2022: where reading inputs takes way more time than solving the puzzle!

So… here we start!

The gist of the input is that there are paragraphs, each one cointaining a collection of integers. It’s somehow clear that each collection should be handled separately.

As I’m still very new to Raku, I just know that I don’t know a lot about how to be efficient to do stuff, especially input and output. Here’s what burned most of my time for getting to the solution of the first part:

sub get-inputs ($filename) {
   my @list-for = [], ;
   for $filename.IO.lines -> $line {
      if $line ~~ /^ \s* $/ { @list-for.push: [] }
      else { @list-for[*-1].push: $line.Int }
   @list-for.pop unless @list-for[*-1].elems;
   return @list-for;

What a mess. My strong Perl accent is immediately recognizable.

To really learn something, we can draw inspiration from 0rac1e’s solution and write this instead:

sub get-inputs ($filename) {

I admit that I still have to get the hang of it when it comes to turning stuff into arrays. I was forced to add the ».Array because I got error messages about sequences being already used, but I can’t understand then why the following is giving the same error:

sub get-inputs ($filename) {

I suspect that the error is at the outer level this time.


The first part of the puzzle is very straightforward: find the collection with the highest sum. This is short and sweet:

sub part1 ($inputs) { $inputs».sum.max }

I really like when I can use hyperoperators and I really like that I have « and » easily mapped in my keyboard. So snob.

The second part is about finding the sum of the three collections with the highest sum. This is my approach:

  • calculate the sum of each collection, like before
  • sort them in descending order
  • take the sum of the first three elements.
sub part2 ($inputs) { $inputs».sum.sort.reverse[0..2].sum }

The annoying part here is that sorting is in ascending order by default, so I’m using reverse mainly for readability (I could have played with fancier indexes instead of [0..2] and spare the reverse).

But, of course… This! Is! Raku!

So kudos to liztormato for chiming in and suggesting that there is indeed a small aptly-shaped tool that is fit for this need, as expressed in this hint:

sub part2 ($inputs) { $inputs».sum.sort.tail(3).sum }

What can I say? Day one is supposed to get some rust off, and I’m already learning a lot.


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