Day 1: Historian Hysteria
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4 points
Rust
Right IDs are directly read into a hash map counter.
use std::str::FromStr;
use std::collections::HashMap;
fn part1(input: String) {
let mut left = Vec::new();
let mut right = Vec::new();
for line in input.lines() {
let mut parts = line.split_whitespace()
.map(|p| u32::from_str(p).unwrap());
left.push(parts.next().unwrap());
right.push(parts.next().unwrap());
}
left.sort_unstable();
right.sort_unstable();
let diff: u32 = left.iter().zip(right)
.map(|(l, r)| l.abs_diff(r))
.sum();
println!("{diff}");
}
fn part2(input: String) {
let mut left = Vec::new();
let mut right: HashMap<u32, u32> = HashMap::new();
for line in input.lines() {
let mut parts = line.split_whitespace()
.map(|p| u32::from_str(p).unwrap());
left.push(parts.next().unwrap());
*right.entry(parts.next().unwrap()).or_default() += 1;
}
let similar: u32 = left.iter()
.map(|n| n * right.get(n).copied().unwrap_or_default())
.sum();
println!("{similar}");
}
util::aoc_main!();