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Advent of Code: Day Three

Spoilers for Advent of Code below

Day three, checked off ✅. I'm rapidly closing in on a high score here (although that's only Day 4, so it's a very low bar).

This wasn't too much of a challenge either, the IterTools crate gave me some useful helpers that made parsing the data slightly easier, and HashMaps means I could pretty quickly construct a unique set of data.

To calculate the score, I was lazy. I constructed a string containing every character a-zA-Z, and just used the index of a character + 1:

fn score_char(character: &char) -> i32 {
    let mut priorities = "abcdefghijklmnopqrstuvwxyzABCDEFGHIJKLMNOPQRSTUVWXYZ".chars();
    (priorities.position(|c| c == *character).unwrap() as i32) + 1
}

Dead simple, and works well. Will break dramatically if an unexpected character is entered (well, it'll panic anyway). PArt two was more-or-less the same, I just needed to write some extra code to produce chunks of data (spoiler: I used iter.chunk):

pub fn group_and_score(inputs: Vec<String>) -> i32 {
    inputs
        .chunks_exact(3)
        .map(|chunk| {
            ElfGroup::from_lines([
                String::from(&chunk[0]),
                String::from(&chunk[1]),
                String::from(&chunk[2]),
            ])
            .score
        })
        .sum()
}

I'm quite enjoying this so far, let's see what Day 4 brings.