Year 2024 Day 3

Author: maneatingape

README.md

@@ -79,6 +79,7 @@ Performance is reasonable even on older hardware, for example a 2011 MacBook Pro
 | --- | --- | --- | --: |
 | 1 | [Historian Hysteria](https://adventofcode.com/2024/day/1) | [Source](src/year2024/day01.rs) | 21 |
 | 2 | [Red-Nosed Reports](https://adventofcode.com/2024/day/2) | [Source](src/year2024/day02.rs) | 43 |
+| 3 | [Mull It Over](https://adventofcode.com/2024/day/3) | [Source](src/year2024/day03.rs) | 13 |
 
 ## 2023
 

benches/benchmark.rs

@@ -294,4 +294,5 @@ mod year2023 {
 mod year2024 {
     benchmark!(year2024, day01);
     benchmark!(year2024, day02);
+    benchmark!(year2024, day03);
 }

src/lib.rs

@@ -293,4 +293,5 @@ pub mod year2023 {
 pub mod year2024 {
     pub mod day01;
     pub mod day02;
+    pub mod day03;
 }

src/main.rs

@@ -360,5 +360,5 @@ fn year2023() -> Vec<Solution> {
 }
 
 fn year2024() -> Vec<Solution> {
-    vec![solution!(year2024, day01), solution!(year2024, day02)]
+    vec![solution!(year2024, day01), solution!(year2024, day02), solution!(year2024, day03)]
 }

src/year2024/day03.rs

@@ -0,0 +1,76 @@
+type Input = (u32, u32);
+
+pub fn parse(input: &str) -> Input {
+    let memory = input.as_bytes();
+    let mut index = 0;
+    let mut enabled = true;
+    let mut part_one = 0;
+    let mut part_two = 0;
+
+    while index < memory.len() {
+        // Prefixes
+        if memory[index..].starts_with(b"mul(") {
+            index += 4;
+        } else if memory[index..].starts_with(b"do()") {
+            index += 4;
+            enabled = true;
+            continue;
+        } else if memory[index..].starts_with(b"don't()") {
+            index += 7;
+            enabled = false;
+            continue;
+        } else {
+            index += 1;
+            continue;
+        }
+
+        // First numnber
+        let mut first = 0;
+        let mut digits = 0;
+
+        while memory[index].is_ascii_digit() {
+            first = 10 * first + (memory[index] - b'0') as u32;
+            digits += 1;
+            index += 1;
+        }
+
+        // Middle
+        if digits == 0 || memory[index] != b',' {
+            continue;
+        }
+        index += 1;
+
+        // Second
+        let mut second = 0;
+        let mut digits = 0;
+
+        while memory[index].is_ascii_digit() {
+            second = 10 * second + (memory[index] - b'0') as u32;
+            digits += 1;
+            index += 1;
+        }
+
+        // Suffix
+        if digits == 0 || memory[index] != b')' {
+            continue;
+        }
+        index += 1;
+
+        // Multiply
+        let product = first * second;
+        part_one += product;
+        if enabled {
+            part_two += product;
+        }
+    }
+
+    (part_one, part_two)
+}
+
+pub fn part1(input: &Input) -> u32 {
+    input.0
+}
+
+pub fn part2(input: &Input) -> u32 {
+    input.1
+}

tests/test.rs

@@ -283,4 +283,5 @@ mod year2023 {
 mod year2024 {
     mod day01_test;
     mod day02_test;
+    mod day03_test;
 }

tests/year2024/day03_test.rs

@@ -0,0 +1,19 @@
+use aoc::year2024::day03::*;
+
+const FIRST_EXAMPLE: &str = "\
+xmul(2,4)%&mul[3,7]!@^do_not_mul(5,5)+mul(32,64]then(mul(11,8)mul(8,5))";
+
+const SECOND_EXAMPLE: &str = "\
+xmul(2,4)&mul[3,7]!^don't()_mul(5,5)+mul(32,64](mul(11,8)undo()?mul(8,5))";
+
+#[test]
+fn part1_test() {
+    let input = parse(FIRST_EXAMPLE);
+    assert_eq!(part1(&input), 161);
+}
+
+#[test]
+fn part2_test() {
+    let input = parse(SECOND_EXAMPLE);
+    assert_eq!(part2(&input), 48);
+}