Year 2024 Day 2

Author: maneatingape

README.md

@@ -78,6 +78,7 @@ Performance is reasonable even on older hardware, for example a 2011 MacBook Pro
 | Day | Problem | Solution | Benchmark (μs) |
 | --- | --- | --- | --: |
 | 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) | 85 |
 
 ## 2023
 

benches/benchmark.rs

@@ -293,4 +293,5 @@ mod year2023 {
 
 mod year2024 {
     benchmark!(year2024, day01);
+    benchmark!(year2024, day02);
 }

src/lib.rs

@@ -292,4 +292,5 @@ pub mod year2023 {
 /// # Locate the Chief Historian in time for the big Christmas sleigh launch.
 pub mod year2024 {
     pub mod day01;
+    pub mod day02;
 }

src/main.rs

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

src/year2024/day02.rs

@@ -0,0 +1,56 @@
+//! # Red-Nosed Reports
+use crate::util::parse::*;
+
+type Input = (u32, u32);
+
+pub fn parse(input: &str) -> Input {
+    let mut row = Vec::new();
+    let mut part_one = 0;
+    let mut part_two = 0;
+
+    for line in input.lines() {
+        row.extend(line.iter_unsigned::<u32>());
+
+        if safe(&row) {
+            part_one += 1;
+            part_two += 1;
+        } else {
+            for i in 0..row.len() {
+                let level = row.remove(i);
+
+                if safe(&row) {
+                    part_two += 1;
+                    break;
+                }
+
+                row.insert(i, level);
+            }
+        }
+
+        row.clear();
+    }
+
+    (part_one, part_two)
+}
+
+pub fn part1(input: &Input) -> u32 {
+    input.0
+}
+
+pub fn part2(input: &Input) -> u32 {
+    input.1
+}
+
+fn safe(levels: &[u32]) -> bool {
+    let mut up = true;
+    let mut down = true;
+    let mut range = true;
+
+    for w in levels.windows(2) {
+        up &= w[0] < w[1];
+        down &= w[0] > w[1];
+        range &= (1..=3).contains(&w[0].abs_diff(w[1]));
+    }
+
+    (up ^ down) && range
+}

tests/test.rs

@@ -282,4 +282,5 @@ mod year2023 {
 
 mod year2024 {
     mod day01_test;
+    mod day02_test;
 }

tests/year2024/day02_test.rs

@@ -0,0 +1,21 @@
+use aoc::year2024::day02::*;
+
+const EXAMPLE: &str = "\
+7 6 4 2 1
+1 2 7 8 9
+9 7 6 2 1
+1 3 2 4 5
+8 6 4 4 1
+1 3 6 7 9";
+
+#[test]
+fn part1_test() {
+    let input = parse(EXAMPLE);
+    assert_eq!(part1(&input), 2);
+}
+
+#[test]
+fn part2_test() {
+    let input = parse(EXAMPLE);
+    assert_eq!(part2(&input), 4);
+}