day 3

Cargo.lock

@@ -2,13 +2,29 @@
 # It is not intended for manual editing.
 version = 4
 
+[[package]]
+name = "aho-corasick"
+version = "1.1.3"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "8e60d3430d3a69478ad0993f19238d2df97c507009a52b3c10addcd7f6bcb916"
+dependencies = [
+ "memchr",
+]
+
 [[package]]
 name = "aoc2024"
 version = "0.1.0"
 dependencies = [
+ "regex",
  "thiserror",
 ]
 
+[[package]]
+name = "memchr"
+version = "2.7.4"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "78ca9ab1a0babb1e7d5695e3530886289c18cf2f87ec19a575a0abdce112e3a3"
+
 [[package]]
 name = "proc-macro2"
 version = "1.0.92"
@@ -27,6 +43,35 @@ dependencies = [
  "proc-macro2",
 ]
 
+[[package]]
+name = "regex"
+version = "1.11.1"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "b544ef1b4eac5dc2db33ea63606ae9ffcfac26c1416a2806ae0bf5f56b201191"
+dependencies = [
+ "aho-corasick",
+ "memchr",
+ "regex-automata",
+ "regex-syntax",
+]
+
+[[package]]
+name = "regex-automata"
+version = "0.4.9"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "809e8dc61f6de73b46c85f4c96486310fe304c434cfa43669d7b40f711150908"
+dependencies = [
+ "aho-corasick",
+ "memchr",
+ "regex-syntax",
+]
+
+[[package]]
+name = "regex-syntax"
+version = "0.8.5"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "2b15c43186be67a4fd63bee50d0303afffcef381492ebe2c5d87f324e1b8815c"
+
 [[package]]
 name = "syn"
 version = "2.0.90"

Cargo.toml

@@ -4,4 +4,5 @@
     version = "0.1.0"
 
 [dependencies]
+    regex     = "1"
     thiserror = "2"

src/main.rs

@@ -1 +1,7 @@
-fn main() {}
+use aoc2024::solutions::{day_3::AocDayThreeSolution, AocSolution};
+
+fn main() {
+    let sol = AocDayThreeSolution;
+
+    println!("p1: {}\np2: {}", sol.part_one(), sol.part_two())
+}

src/solutions/day_3.rs

@@ -0,0 +1,51 @@
+use std::sync::LazyLock;
+
+use regex::Regex;
+
+use super::AocSolution;
+
+static MUL: LazyLock<Regex> =
+    LazyLock::new(|| Regex::new(r"mul\([0-9]{1,3},[0-9]{1,3}\)").unwrap());
+
+static COND_MUL: LazyLock<Regex> =
+    LazyLock::new(|| Regex::new(r"(mul\([0-9]{1,3},[0-9]{1,3}\))|(do\(\))|(don't\(\))").unwrap());
+
+#[derive(Clone, Copy)]
+pub struct AocDayThreeSolution;
+
+fn as_mul(s: &str) -> u64 {
+    let (a, b) = s[4..(s.len() - 1)]
+        .split_once(',')
+        .map(|(a, b)| (a.parse::<u64>().unwrap(), b.parse::<u64>().unwrap()))
+        .unwrap();
+
+    a * b
+}
+
+impl AocSolution for AocDayThreeSolution {
+    type Output = u64;
+    const INPUT: &str = include_str!("../../input/day3.txt");
+
+    fn part_one(&self) -> Self::Output {
+        MUL.find_iter(Self::INPUT)
+            .map(|x| x.as_str())
+            .map(as_mul)
+            .sum()
+    }
+
+    fn part_two(&self) -> Self::Output {
+        COND_MUL
+            .find_iter(Self::INPUT)
+            .map(|x| x.as_str())
+            .fold((0, true), |(sum, flag), cut| {
+                if cut.starts_with("mul") && flag {
+                    (sum + as_mul(cut), flag)
+                } else if cut == "do()" {
+                    (sum, true)
+                } else {
+                    (sum, false)
+                }
+            })
+            .0
+    }
+}

src/solutions/mod.rs

@@ -1,5 +1,13 @@
-pub mod day_1;
-pub mod day_2;
+macro_rules! define_solution {
+    ($($id:ident),+ $(,)?) => {
+        $(pub mod $id;)+
+    };
+}
+
+define_solution!(
+    day_1, day_2, day_3, day_4, day_5, day_6, day_7, day_8, day_9, day_10, day_11, day_12, day_13,
+    day_14, day_15, day_16, day_17, day_18, day_19, day_20, day_21, day_22, day_23, day_24, day_25,
+);
 
 pub trait AocSolution {
     type Output;