diff --git a/src/day3.rs b/src/day3.rs
new file mode 100644
index 0000000..dce28e0
--- /dev/null
+++ b/src/day3.rs
@@ -0,0 +1,113 @@
+use aoc_runner_derive::{aoc, aoc_generator};
+use itertools::Itertools;
+use std::fmt::Display;
+
+struct Rucksack {
+    items: Vec<u8>,
+}
+
+impl From<&[u8]> for Rucksack {
+    fn from(s: &[u8]) -> Self {
+        Self {
+            items: s.iter().cloned().collect(),
+        }
+    }
+}
+
+impl Display for Rucksack {
+    fn fmt(&self, f: &mut std::fmt::Formatter<'_>) -> std::fmt::Result {
+        f.write_fmt(format_args!(
+            "{}{}",
+            String::from_utf8_lossy(&self.compartments()[0]),
+            String::from_utf8_lossy(&self.compartments()[1])
+        ))
+    }
+}
+
+impl Rucksack {
+    fn compartments(&self) -> [&[u8]; 2] {
+        let tup = self.items.split_at(self.items.len() / 2);
+        [tup.0, tup.1]
+    }
+    fn common(&self) -> u8 {
+        for item in self.compartments()[0] {
+            if self.compartments()[1].contains(&item) {
+                return *item;
+            }
+        }
+        panic!("Common item not found");
+    }
+    fn contains(&self, item: &u8) -> bool {
+        self.compartments().into_iter().flatten().contains(item)
+    }
+    fn common_with<'a>(&self, other: &[u8]) -> impl Iterator<Item = u8> {
+        self.compartments()
+            .into_iter()
+            .flatten()
+            .filter(|c| other.contains(c))
+            .cloned()
+    }
+}
+
+fn priority(c: u8) -> u8 {
+    if c >= b'A' && c <= b'Z' {
+        c - b'A' + 27
+    } else if c >= b'a' && c <= b'z' {
+        c - b'a' + 1
+    } else {
+        panic!("Invalid item {c}")
+    }
+}
+
+#[aoc_generator(day3)]
+fn parse(input: &[u8]) -> Vec<Rucksack> {
+    input.split(|i| *i == b'\n').map(|x| x.into()).collect()
+}
+
+#[aoc(day3, part1)]
+fn part1(input: &Vec<Rucksack>) -> u64 {
+    input.iter().map(|sack| priority(sack.common()) as u64).sum()
+}
+
+#[aoc(day3, part2)]
+fn part2(input: &Vec<Rucksack>) -> u64 {
+    let mut total = 0u64;
+    for sacks in input.chunks(3) {
+        let commons_1 = sacks[0].common_with(&sacks[1].items).unique().collect_vec();
+        let commons = sacks[2].common_with(&commons_1).unique().collect_vec();
+
+        if commons.len() != 1 {
+            panic!(
+                "Wrong number ({}) of commons for sacks {} {} {}",
+                commons.len(),
+                sacks[0],
+                sacks[1],
+                sacks[2]
+            );
+        }
+        total += priority(commons[0]) as u64
+    }
+    total
+}
+
+#[cfg(test)]
+mod tests {
+    use super::*;
+
+    const EXAMPLE: &[u8] = b"vJrwpWtwJgWrhcsFMMfFFhFp
+jqHRNqRjqzjGDLGLrsFMfFZSrLrFZsSL
+PmmdzqPrVvPwwTWBwg
+wMqvLMZHhHMvwLHjbvcjnnSBnvTQFn
+ttgJtRGJQctTZtZT
+CrZsJsPPZsGzwwsLwLmpwMDw";
+
+    #[test]
+    fn part1_example() {
+        assert_eq!(part1(&parse(EXAMPLE)), 157);
+    }
+
+    #[test]
+    fn part2_example() {
+        assert_eq!(part2(&parse(EXAMPLE)), 70);
+    }
+}
diff --git a/src/lib.rs b/src/lib.rs
index 9cca356..72cdbc0 100644
--- a/src/lib.rs
+++ b/src/lib.rs
@@ -1,7 +1,8 @@
-mod day2;
 mod day1;
+mod day2;
+mod day3;
 use aoc_runner_derive::aoc_lib;
 
-pub mod day6;
+mod day6;
 
 aoc_lib! { year = 2022 }