Do day 3

Cargo.toml

@@ -6,3 +6,4 @@ edition = "2021"
 
 [dependencies]
 itertools = "0.13"
+regex = "1"

src/day03/example1.txt

@@ -0,0 +1 @@
+xmul(2,4)%&mul[3,7]!@^do_not_mul(5,5)+mul(32,64]then(mul(11,8)mul(8,5))

src/day03/example2.txt

@@ -0,0 +1 @@
+xmul(2,4)&mul[3,7]!^don't()_mul(5,5)+mul(32,64](mul(11,8)undo()?mul(8,5))

src/day03/mod.rs

@@ -0,0 +1,57 @@
+use regex::{Captures, Regex};
+
+fn parse_mul(caps: Captures) -> usize {
+    caps[1].parse::<usize>().unwrap() * caps[2].parse::<usize>().unwrap()
+}
+
+pub fn puzzle1(input: &str) -> usize {
+    let re = Regex::new(r"mul\((\d+),(\d+)\)");
+    re.unwrap().captures_iter(input).map(parse_mul).sum()
+}
+
+pub fn puzzle2(input: &str) -> usize {
+    let mut sum = 0;
+    let mut enabled = true;
+    let re = Regex::new(r"mul\((\d+),(\d+)\)|do\(\)|don't\(\)");
+    for caps in re.unwrap().captures_iter(input) {
+        match &caps[0] {
+            "do()" => enabled = true,
+            "don't()" => enabled = false,
+            _ => {
+                if enabled {
+                    sum += parse_mul(caps);
+                }
+            }
+        }
+    }
+    sum
+}
+
+#[cfg(test)]
+mod tests {
+    use super::*;
+
+    const EXAMPLE1: &str = include_str!("example1.txt");
+    const EXAMPLE2: &str = include_str!("example2.txt");
+    const INPUT: &str = include_str!("input.txt");
+
+    #[test]
+    fn test_puzzle1_example1() {
+        assert_eq!(puzzle1(EXAMPLE1), 161);
+    }
+
+    #[test]
+    fn test_puzzle1_input() {
+        assert_eq!(puzzle1(INPUT), 174103751);
+    }
+
+    #[test]
+    fn test_puzzle2_example2() {
+        assert_eq!(puzzle2(EXAMPLE2), 48);
+    }
+
+    #[test]
+    fn test_puzzle2_input() {
+        assert_eq!(puzzle2(INPUT), 100411201);
+    }
+}

src/main.rs

@@ -1,5 +1,6 @@
 mod day01;
 mod day02;
+mod day03;
 
 use std::{env, fs};
 
@@ -15,6 +16,9 @@ fn main() {
         (2, 1) => day02::puzzle1(&input).to_string(),
         (2, 2) => day02::puzzle2(&input).to_string(),
 
+        (3, 1) => day03::puzzle1(&input).to_string(),
+        (3, 2) => day03::puzzle2(&input).to_string(),
+
         _ => panic!("no puzzle {} for day {}", puzzle, day),
     };
     println!("{}", answer.trim_end());