1 files changed, 62 insertions, 0 deletions
diff --git a/src/bin/2022/day3.rs b/src/bin/2022/day3.rs
new file mode 100644
index 0000000..a56baf4
--- /dev/null
+++ b/src/bin/2022/day3.rs
@@ -0,0 +1,62 @@
+#![allow(dead_code)]
+#![allow(unused_variables)]
+
+use advent_of_code::prelude::*;
+
+pub fn parse(
+    fh: File,
+) -> Result<impl Iterator<Item = (HashSet<char>, HashSet<char>)>> {
+    Ok(parse::raw_lines(fh).map(|line| {
+        let (first, second) = line.split_at(line.len() / 2);
+        let first: HashSet<char> = first.chars().collect();
+        let second: HashSet<char> = second.chars().collect();
+        (first, second)
+    }))
+}
+
+pub fn part1(
+    sacks: impl Iterator<Item = (HashSet<char>, HashSet<char>)>,
+) -> Result<u32> {
+    Ok(sacks
+        .map(|(first, second)| {
+            priority(*first.intersection(&second).next().unwrap())
+        })
+        .sum())
+}
+
+pub fn part2(
+    mut sacks: impl Iterator<Item = (HashSet<char>, HashSet<char>)>,
+) -> Result<u32> {
+    let mut total = 0;
+    while let (Some(first), Some(second), Some(third)) =
+        (sacks.next(), sacks.next(), sacks.next())
+    {
+        let first: HashSet<char> = first.0.union(&first.1).copied().collect();
+        let second: HashSet<char> =
+            second.0.union(&second.1).copied().collect();
+        let third: HashSet<char> = third.0.union(&third.1).copied().collect();
+        total +=
+            priority(*(&(&first & &second) & &third).iter().next().unwrap());
+    }
+    Ok(total)
+}
+
+fn priority(c: char) -> u32 {
+    match c {
+        'a'..='z' => u32::from(c) - u32::from('a') + 1,
+        'A'..='Z' => u32::from(c) - u32::from('A') + 27,
+        _ => unreachable!(),
+    }
+}
+
+#[test]
+fn test() {
+    assert_eq!(
+        part1(parse(parse::data(2022, 3).unwrap()).unwrap()).unwrap(),
+        8493
+    );
+    assert_eq!(
+        part2(parse(parse::data(2022, 3).unwrap()).unwrap()).unwrap(),
+        2552
+    );
+}