feat(day3): init

src/solutions/day_03.rs

@@ -0,0 +1,54 @@
+use itertools::Itertools;
+use regex::Regex;
+
+use crate::common::{Answer, Solution};
+
+pub struct Day03;
+
+impl Solution for Day03 {
+    fn name(&self) -> &'static str {
+        "Mull It Over"
+    }
+
+    fn part_a(&self, input: &str) -> Answer {
+        let re = Regex::new(r"mul\((\d+),(\d+)\)").unwrap();
+
+        let sum = re
+            .captures_iter(input)
+            .map(|c| c.extract())
+            .map(|(_, [a, b])| a.parse::<u64>().unwrap() * b.parse::<u64>().unwrap())
+            .sum::<u64>();
+
+        Answer::Number(sum)
+    }
+
+    fn part_b(&self, input: &str) -> Answer {
+        let without_donts = input
+            .split("do()")
+            .map(|s| s.split_once("don't()").map(|(b, _)| b).unwrap_or(s))
+            .join("");
+
+        self.part_a(&without_donts)
+    }
+}
+
+#[cfg(test)]
+mod test {
+    use super::Day03;
+    use crate::common::Solution;
+
+    const INPUT_A: &str = "xmul(2,4)%&mul[3,7]!@^do_not_mul(5,5)+mul(32,64]then(mul(11,8)mul(8,5))";
+
+    const INPUT_B: &str =
+        "xmul(2,4)&mul[3,7]!^don't()_mul(5,5)+mul(32,64](mul(11,8)undo()?mul(8,5))";
+
+    #[test]
+    fn part_a() {
+        assert_eq!(Day03.part_a(INPUT_A), 161.into());
+    }
+
+    #[test]
+    fn part_b() {
+        assert_eq!(Day03.part_b(INPUT_B), 48.into());
+    }
+}

src/solutions/mod.rs

@@ -2,5 +2,6 @@ use crate::common::Solution;
 
 mod day_01;
 mod day_02;
+mod day_03;
 
-pub const SOLUTIONS: &[&dyn Solution] = &[&day_01::Day01, &day_02::Day02];
+pub const SOLUTIONS: &[&dyn Solution] = &[&day_01::Day01, &day_02::Day02, &day_03::Day03];