Merge pull request #13 from ephemient/rs/day2

README.md

@@ -6,4 +6,4 @@ Development occurs in language-specific directories:
 |[Haskell](hs) ![Haskell CI](https://github.com/ephemient/aoc2024/workflows/Haskell%20CI/badge.svg)|[Kotlin](kt) ![Kotlin CI](https://github.com/ephemient/aoc2024/workflows/Kotlin%20CI/badge.svg)|[Python](py) ![Python CI](https://github.com/ephemient/aoc2024/workflows/Python%20CI/badge.svg)|[Rust](rs) ![Rust CI](https://github.com/ephemient/aoc2024/workflows/Rust%20CI/badge.svg)|
 |--:|--:|--:|--:|
 |[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.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)|

rs/benches/criterion.rs

@@ -1,4 +1,4 @@
-use aoc2024::day1;
+use aoc2024::{day1, day2};
 use criterion::{black_box, Criterion};
 use std::env;
 use std::fs;
@@ -20,6 +20,12 @@ fn aoc2024_bench(c: &mut Criterion) -> io::Result<()> {
     g.bench_function("part 2", |b| b.iter(|| day1::part2(black_box(&data))));
     g.finish();
 
+    let data = get_day_input(2)?;
+    let mut g = c.benchmark_group("day 2");
+    g.bench_function("part 1", |b| b.iter(|| day2::part1(black_box(&data))));
+    g.bench_function("part 2", |b| b.iter(|| day2::part2(black_box(&data))));
+    g.finish();
+
     Ok(())
 }
 

rs/src/day2.rs

@@ -0,0 +1,81 @@
+fn parse(data: &str) -> Vec<Vec<i32>> {
+    data.lines()
+        .flat_map(|line| {
+            line.split_ascii_whitespace()
+                .map(|level| level.parse::<i32>().ok())
+                .collect::<Option<Vec<_>>>()
+        })
+        .collect::<Vec<_>>()
+}
+
+fn is_safe_1(report: &[i32]) -> bool {
+    let mut decreasing = false;
+    let mut increasing = false;
+    report
+        .iter()
+        .zip(report.iter().skip(1))
+        .all(|(x, y)| match x - y {
+            -3..=-1 => {
+                decreasing = true;
+                !increasing
+            }
+            1..=3 => {
+                increasing = true;
+                !decreasing
+            }
+            _ => false,
+        })
+}
+
+fn is_safe_2(report: &[i32]) -> bool {
+    if report.is_empty() {
+        return true;
+    }
+    let mut report2 = vec![0; report.len() - 1];
+    report2.copy_from_slice(&report[1..]);
+    is_safe_1(&report2)
+        || (0..report2.len()).any(|i| {
+            report2[i] = report[i];
+            is_safe_1(&report2)
+        })
+}
+
+pub fn part1(data: &str) -> usize {
+    parse(data)
+        .into_iter()
+        .filter(|report| is_safe_1(report))
+        .count()
+}
+
+pub fn part2(data: &str) -> usize {
+    parse(data)
+        .into_iter()
+        .filter(|report| is_safe_2(report))
+        .count()
+}
+
+#[cfg(test)]
+mod tests {
+    use super::*;
+    use indoc::indoc;
+    use pretty_assertions::assert_eq;
+
+    static EXAMPLE: &str = indoc! {"
+        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_examples() {
+        assert_eq!(2, part1(EXAMPLE));
+    }
+
+    #[test]
+    fn part2_examples() {
+        assert_eq!(4, part2(EXAMPLE));
+    }
+}

rs/src/lib.rs

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

rs/src/main.rs

@@ -1,4 +1,4 @@
-use aoc2024::day1;
+use aoc2024::{day1, day2};
 use std::collections::HashSet;
 use std::env;
 use std::fs;
@@ -24,5 +24,13 @@ fn main() -> io::Result<()> {
         println!();
     }
 
+    if args.is_empty() || args.contains("2") {
+        println!("Day 2");
+        let data = get_day_input(2)?;
+        println!("{:?}", day2::part1(&data));
+        println!("{:?}", day2::part2(&data));
+        println!();
+    }
+
     Ok(())
 }