days 1-3

src/bin/03.rs

@@ -0,0 +1,60 @@
+advent_of_code::solution!(3);
+use regex::Regex;
+
+pub fn part_one(input: &str) -> Option<u32> {
+    let mul_regex = Regex::new(r"mul\((\d\d?\d?),(\d\d?\d?)\)").unwrap();
+
+    let result = mul_regex.captures_iter(input).fold(0, |total, cap| {
+        let (_, [a_str, b_str]) = cap.extract();
+
+        let a = a_str.parse::<u32>().unwrap();
+        let b = b_str.parse::<u32>().unwrap();
+        let product = a * b;
+
+        return total + product;
+    });
+
+    return Some(result);
+}
+
+pub fn part_two(input: &str) -> Option<u32> {
+    let mul_regex = Regex::new(r"(do)\(\)()()|(don\'t)\(\)()()|(mul)\((\d\d?\d?),(\d\d?\d?)\)").unwrap();
+
+    let (_, result) = mul_regex.captures_iter(input).fold((true, 0), |(enabled, total), cap| {
+        let (_, [command, a_str, b_str]) = cap.extract();
+        // println!("Captures: {command} ({a_str}, {b_str})");
+
+        match command {
+            "do" => return (true, total),
+            "don't" => return (false, total),
+            "mul" => {
+                if !enabled { return (enabled, total) };
+
+                let a = a_str.parse::<u32>().unwrap();
+                let b = b_str.parse::<u32>().unwrap();
+                let product = a * b;
+                return (enabled, total + product)
+            },
+            _ => panic!("Could not match command {command}"),
+        }
+    });
+
+    return Some(result);
+}
+
+#[cfg(test)]
+mod tests {
+    use super::*;
+
+    #[test]
+    fn test_part_one() {
+        let result = part_one(&advent_of_code::template::read_file("examples", DAY));
+        assert_eq!(result, Some(161));
+    }
+
+    #[test]
+    fn test_part_two() {
+        let result = part_two(&advent_of_code::template::read_file_part("examples", DAY, 2));
+        assert_eq!(result, Some(48));
+    }
+}