Day 3: Mull It Over

README.md

@@ -7,4 +7,4 @@ Development occurs in language-specific directories:
 |--:|--:|--:|--:|
 |[Day1.hs](hs/src/Day1.hs)|[Day1.kt](kt/aoc2024-lib/src/commonMain/kotlin/com/github/ephemient/aoc2024/Day1.kt)|[day1.py](py/aoc2024/day1.py)|[day1.rs](rs/src/day1.rs)|
 |[Day2.hs](hs/src/Day2.hs)|[Day2.kt](kt/aoc2024-lib/src/commonMain/kotlin/com/github/ephemient/aoc2024/Day2.kt)|[day2.py](py/aoc2024/day2.py)|[day2.rs](rs/src/day2.rs)|
-|[Day3.hs](hs/src/Day3.hs)|[Day3.kt](kt/aoc2024-lib/src/commonMain/kotlin/com/github/ephemient/aoc2024/Day3.kt)|[day3.py](py/aoc2024/day3.py)||
+|[Day3.hs](hs/src/Day3.hs)|[Day3.kt](kt/aoc2024-lib/src/commonMain/kotlin/com/github/ephemient/aoc2024/Day3.kt)|[day3.py](py/aoc2024/day3.py)|[day3.rs](rs/src/day3.rs)|

rs/Cargo.toml

@@ -17,6 +17,7 @@ name = "aoc2024"
 path = "src/main.rs"
 
 [dependencies]
+if_chain = "1.0.2"
 itertools = "0.13"
 
 [dev-dependencies]

rs/benches/criterion.rs

@@ -1,4 +1,4 @@
-use aoc2024::{day1, day2};
+use aoc2024::{day1, day2, day3};
 use criterion::{black_box, Criterion};
 use std::env;
 use std::fs;
@@ -26,6 +26,12 @@ fn aoc2024_bench(c: &mut Criterion) -> io::Result<()> {
     g.bench_function("part 2", |b| b.iter(|| day2::part2(black_box(&data))));
     g.finish();
 
+    let data = get_day_input(3)?;
+    let mut g = c.benchmark_group("day 3");
+    g.bench_function("part 1", |b| b.iter(|| day3::part1(black_box(&data))));
+    g.bench_function("part 2", |b| b.iter(|| day3::part2(black_box(&data))));
+    g.finish();
+
     Ok(())
 }
 

rs/src/day3.rs

@@ -0,0 +1,60 @@
+use if_chain::if_chain;
+
+pub fn part1(data: &str) -> i32 {
+    const PREFIX: &str = "mul(";
+
+    let mut data = data;
+    let mut total = 0;
+    while let Some(offset) = data.find(PREFIX) {
+        data = data[offset..].strip_prefix(PREFIX).unwrap();
+        if_chain! {
+            if let Some((a, b)) = data.split_once(',');
+            if let Ok(a) = a.parse::<i32>();
+            if let Some((b, c)) = b.split_once(')');
+            if let Ok(b) = b.parse::<i32>();
+            then {
+                data = c;
+                total += a * b;
+            }
+        }
+    }
+    total
+}
+
+pub fn part2(data: &str) -> i32 {
+    let mut data = data;
+    let mut total = 0;
+    while !data.is_empty() {
+        let end = data.find("don't()").unwrap_or(data.len());
+        total += part1(&data[..end]);
+        let Some(start) = data[end..].find("do()") else {
+            break;
+        };
+        data = &data[end + start..];
+    }
+    total
+}
+
+#[cfg(test)]
+mod tests {
+    use super::*;
+    use indoc::indoc;
+    use pretty_assertions::assert_eq;
+
+    static EXAMPLE1: &str = indoc! {"
+        xmul(2,4)%&mul[3,7]!@^do_not_mul(5,5)+mul(32,64]then(mul(11,8)mul(8,5))
+    "};
+    static EXAMPLE2: &str = indoc! {"
+        xmul(2,4)&mul[3,7]!^don't()_mul(5,5)+mul(32,64](mul(11,8)undo()?mul(8,5))
+    "};
+
+    #[test]
+    fn part1_examples() {
+        assert_eq!(161, part1(EXAMPLE1));
+    }
+
+    #[test]
+    fn part2_examples() {
+        assert_eq!(48, part2(EXAMPLE2));
+    }
+}

rs/src/lib.rs

@@ -1,2 +1,3 @@
 pub mod day1;
 pub mod day2;
+pub mod day3;

rs/src/main.rs

@@ -1,4 +1,4 @@
-use aoc2024::{day1, day2};
+use aoc2024::{day1, day2, day3};
 use std::collections::HashSet;
 use std::env;
 use std::fs;
@@ -32,5 +32,13 @@ fn main() -> io::Result<()> {
         println!();
     }
 
+    if args.is_empty() || args.contains("3") {
+        println!("Day 3");
+        let data = get_day_input(3)?;
+        println!("{:?}", day3::part1(&data));
+        println!("{:?}", day3::part2(&data));
+        println!();
+    }
+
     Ok(())
 }