diff --git a/.aoc-cache/3.txt b/.aoc-cache/3.txt
new file mode 100644
index 0000000..01be6a6
--- /dev/null
+++ b/.aoc-cache/3.txt
@@ -0,0 +1,300 @@
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diff --git a/Cargo.lock b/Cargo.lock
index df53ee0..f89ed33 100644
--- a/Cargo.lock
+++ b/Cargo.lock
@@ -17,12 +17,22 @@ version = "1.0.2"
 source = "registry+https://github.com/rust-lang/crates.io-index"
 checksum = "f26201604c87b1e01bd3d98f8d5d9a8fcbb815e8cedb41ffccbeb4bf593a35fe"
 
+[[package]]
+name = "aho-corasick"
+version = "0.7.20"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "cc936419f96fa211c1b9166887b38e5e40b19958e5b895be7c1f93adec7071ac"
+dependencies = [
+ "memchr",
+]
+
 [[package]]
 name = "aoc-2022"
 version = "0.1.0"
 dependencies = [
  "aoc_proc",
  "color-eyre",
+ "regex",
  "time",
  "ureq",
 ]
@@ -272,6 +282,23 @@ dependencies = [
  "proc-macro2",
 ]
 
+[[package]]
+name = "regex"
+version = "1.7.0"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "e076559ef8e241f2ae3479e36f97bd5741c0330689e217ad51ce2c76808b868a"
+dependencies = [
+ "aho-corasick",
+ "memchr",
+ "regex-syntax",
+]
+
+[[package]]
+name = "regex-syntax"
+version = "0.6.28"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "456c603be3e8d448b072f410900c09faf164fbce2d480456f50eea6e25f9c848"
+
 [[package]]
 name = "ring"
 version = "0.16.20"
diff --git a/Cargo.toml b/Cargo.toml
index 687b16f..26d689b 100644
--- a/Cargo.toml
+++ b/Cargo.toml
@@ -13,3 +13,4 @@ color-eyre = "0.6.2"
 aoc_proc = { path = "aoc_proc" }
 ureq = "2.5.0"
 time = "0.3.17"
+regex = "1.7.0"
diff --git a/src/bin/day_2.rs b/src/bin/day_2.rs
index a645361..b25d671 100644
--- a/src/bin/day_2.rs
+++ b/src/bin/day_2.rs
@@ -1,4 +1,3 @@
-
 use std::str::FromStr;
 
 use aoc_2022::prelude::*;
diff --git a/src/bin/day_3.rs b/src/bin/day_3.rs
new file mode 100644
index 0000000..3ad2014
--- /dev/null
+++ b/src/bin/day_3.rs
@@ -0,0 +1,59 @@
+
+use aoc_2022::prelude::*;
+use regex::Regex;
+
+type Input = Vec<(String, String)>;
+
+fn parse(s: &str) -> Result<Input> {
+    let mut backpacks = vec![];
+    for line in s.lines() {
+        let (part_1, part_2) = line.split_at(line.len() / 2);
+        backpacks.push((part_1.to_owned(), part_2.to_owned()));
+    }
+    Ok(backpacks)
+}
+
+#[aoc(day = 3, parse = parse, test_cases = ["day_3.txt"])]
+fn day_3(input: Input) -> Result<()> {
+    // Part 1
+    let mut sum = 0;
+    for (c1, c2) in &input {
+        let regex = Regex::new(&format!("([{c1}])"))?;
+        let overlap = regex.captures(&c2).expect("there to be an overlap").get(1).expect("there to be an overlap").as_str();
+        let overlap = overlap.chars().nth(0).unwrap();
+        let offset = if overlap.is_ascii_uppercase() {
+            26
+        } else {
+            0
+        };
+        sum += offset + (overlap.to_ascii_uppercase() as usize - 0x40);
+    }
+
+    println!("Part one: {sum}");
+
+    sum = 0;
+    for group in input.chunks_exact(3) {
+        let mut present_in_all = "abcdefghijklmnopqrstuvwxyzABCDEFGHIJKLMNOPQRSTUVWXYZ".to_owned();
+        for (c1, c2) in group {
+            let elf = c1.to_owned() + c2;
+            let re = Regex::new(&format!("([{elf}])"))?;
+            let mut new_present = String::new();
+            for m in re.find_iter(&present_in_all) {
+                new_present.push_str(m.as_str());
+            }
+            present_in_all = new_present;
+        }
+        let badge = present_in_all.chars().nth(0).unwrap();
+        let offset = if badge.is_ascii_uppercase() {
+            26
+        } else {
+            0
+        };
+        sum += offset + (badge.to_ascii_uppercase() as usize - 0x40);
+    }
+
+    // Part 2
+    println!("Part two: {sum}");
+
+    Ok(())
+}
diff --git a/test_cases/day_3.txt b/test_cases/day_3.txt
new file mode 100644
index 0000000..9919ffa
--- /dev/null
+++ b/test_cases/day_3.txt
@@ -0,0 +1,6 @@
+vJrwpWtwJgWrhcsFMMfFFhFp
+jqHRNqRjqzjGDLGLrsFMfFZSrLrFZsSL
+PmmdzqPrVvPwwTWBwg
+wMqvLMZHhHMvwLHjbvcjnnSBnvTQFn
+ttgJtRGJQctTZtZT
+CrZsJsPPZsGzwwsLwLmpwMDw
\ No newline at end of file