2022 Day 3

2022/src/bin/day03.rs

@@ -0,0 +1,52 @@
+use std::collections::HashSet;
+
+use itertools::Itertools;
+
+const INPUT: &str = include_str!("../../input/day03.txt");
+
+fn main() {
+    println!("{}", part1(INPUT));
+    println!("{}", part2(INPUT));
+}
+
+fn part1(input: &str) -> usize {
+    let mut sum = 0;
+    for line in input.split('\n').filter(|l| !l.is_empty()) {
+        let mid = line.len() / 2;
+
+        let l = &line[..mid];
+        let r = &line[mid..];
+
+        let first: HashSet<char> = l.chars().collect();
+        let second: HashSet<char> = r.chars().collect();
+
+        let shared = first.intersection(&second).next().unwrap();
+        sum += priority(shared);
+    }
+    sum
+}
+
+const ALPHABET: &str = "abcdefghijklmnopqrstuvwxyzABCDEFGHIJKLMNOPQRSTUVWXYZ";
+
+fn priority(c: &char) -> usize {
+    1 + ALPHABET.chars().position(|x| x == *c).unwrap_or_default()
+}
+
+fn part2(input: &str) -> usize {
+    let mut sum = 0;
+    let lines = input.split('\n').filter(|l| !l.is_empty());
+    for group in &lines.chunks(3) {
+        let sets: Vec<HashSet<char>> = group
+            .map(|rucksack| rucksack.chars().collect::<HashSet<char>>())
+            .collect();
+
+        let mut shared = sets[0].clone();
+        shared = shared.intersection(&sets[1]).cloned().collect();
+        shared = shared.intersection(&sets[2]).cloned().collect();
+
+        let badge = shared.iter().next().unwrap();
+
+        sum += priority(badge);
+    }
+    sum
+}