advent-of-code/2024/day1

Solution Day 1

Tasks

(This is a technical summary of the tasks without the nice story behind it, so go the the website and look at it yourself for more details)

Task 1

Basically load a CSV-file with two columns, sort the columns individually and sum up the resulting pairs.

Task 2

Slight variation: instead of summing up the pairs, use the first column as a search key to count the occurencences in the second column and then multiply each key with it's number of occurences, summing up the products.

Note: The "key" in the first column can occur multiple times and isn't therefore really a key at all.

Solutions

Both solutions will fail if the format even slightly deviated from the one given in the example. Only numbers, no characters etc. Basically: production code should get rid of the unwrap()s.

Task 1

Straightforward. Will fail horribly at runtime, if the second column has fewer values, that the first. Also: Haskell gurus and other FP cracks will probably haunt me for the use of for .. in .. and mutable variables instead of fold() (which Rust would have. Couldn't be bothered though).

Also I learned, that Rust's Vec<T> has an in-place sort like Javascript. Makes sense from the perspective of a memory-efficient language. Was surprising to me anyway.

Task 2

Arguably more robust than Task 1 because it doesn't assume anything about the size of column 2. Will fail at runtime, if the the number of occurences of a key goes beyond i32 (2^31, so well beyond the realm of the Advent of Code tests)