Complete day 3 part 2

2024/examples/day_3_1.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))

2024/src/solutions/day_3.rs

@@ -17,6 +17,40 @@ pub fn part_one(input: &Parsed) -> Result<u32, String> {
     Ok(total)
 }
 
-pub fn part_two(input: &Parsed) -> Result<usize, String> {
-    Ok(0)
+pub fn part_two(input: &Parsed) -> Result<u32, String> {
+    let re = Regex::new(r"mul\(([0-9]{1,3}),([0-9]{1,3})\)").unwrap();
+    let mut total: u32 = 0;
+
+    let mut start = Some(0);
+    let mut stop_idx;
+    while start.is_some() {
+        let start_idx = start.unwrap();
+        stop_idx = input[start_idx..].find("don't()").and_then(|x| Some(x + start_idx)).unwrap_or(input.len());
+        for (_, [x, y]) in re.captures_iter(&input[start_idx..stop_idx]).map(|c| c.extract()) {
+            total += x.parse::<u32>().unwrap() * y.parse::<u32>().unwrap();
+        }
+        start = input[stop_idx..].find("do()").and_then(|x| Some(x + stop_idx));
+    }
+    Ok(total)
+}
+
+#[cfg(test)]
+mod tests {
+    use super::*;
+
+    #[test]
+    fn test_part1() {
+        let example = include_str!("../../examples/day_3_1.txt");
+        let parsed = parse(example).unwrap();
+        let solution = part_one(&parsed);
+        assert_eq!(solution, Ok(161));
+    }
+
+    #[test]
+    fn test_part2() {
+        let example = include_str!("../../examples/day_3_1.txt");
+        let parsed = parse(example).unwrap();
+        let solution = part_two(&parsed);
+        assert_eq!(solution, Ok(48));
+    }
 }