Day 01 - Historian Hysteria

Language: Rust

Problem https://adventofcode.com/2024/day/1

Part 1: Two columns of numbers. Parse them into two separate vecs, sort both, then pair them up smallest to smallest and sum the absolute differences:

for pair in input.lines() {
    let mut parts = pair.split_whitespace();
    if let (Some(a), Some(b)) = (parts.next(), parts.next()) {
        if let (Ok(num_a), Ok(num_b)) = (a.parse::<i32>(), b.parse::<i32>()) {
            v1.push(num_a);
            v2.push(num_b);
        }
    }
}

v1.sort();
v2.sort();

let ans: i32 = v1.iter()
    .zip(v2.iter())
    .map(|(&a, &b)| (a - b).abs())
    .sum::<i32>();

Part 2: For each number in the left list, count how many times it appears in the right list and multiply. I iterate v2 for each element in v1 and accumulate the score:

for num in v1 {
    let count = v2.iter().filter(|x| **x == num).count() as i32;
    sum += num * count;
}

Solution: https://github.com/Elyrial/AdventOfCode/blob/main/src/solutions/year2024/day01.rs

No C writeup yet.