Merge pull request #113 from ephemient/rs/day14

Day 14: Restroom Redoubt

README.md

@@ -18,7 +18,7 @@ Development occurs in language-specific directories:
 |[Day11.hs](hs/src/Day11.hs)|[Day11.kt](kt/aoc2024-lib/src/commonMain/kotlin/com/github/ephemient/aoc2024/Day11.kt)|[day11.py](py/aoc2024/day11.py)|[day11.rs](rs/src/day11.rs)|
 |[Day12.hs](hs/src/Day12.hs)|[Day12.kt](kt/aoc2024-lib/src/commonMain/kotlin/com/github/ephemient/aoc2024/Day12.kt)|[day12.py](py/aoc2024/day12.py)|[day12.rs](rs/src/day12.rs)|
 |[Day13.hs](hs/src/Day13.hs)|[Day13.kt](kt/aoc2024-lib/src/commonMain/kotlin/com/github/ephemient/aoc2024/Day13.kt)|[day13.py](py/aoc2024/day13.py)|[day13.rs](rs/src/day13.rs)|
-|[Day14.hs](hs/src/Day14.hs)|[Day14.kt](kt/aoc2024-lib/src/commonMain/kotlin/com/github/ephemient/aoc2024/Day14.kt)|[day14.py](py/aoc2024/day14.py)||
+|[Day14.hs](hs/src/Day14.hs)|[Day14.kt](kt/aoc2024-lib/src/commonMain/kotlin/com/github/ephemient/aoc2024/Day14.kt)|[day14.py](py/aoc2024/day14.py)|[day14.rs](rs/src/day14.rs)|
 |[Day15.hs](hs/src/Day15.hs)|[Day15.kt](kt/aoc2024-lib/src/commonMain/kotlin/com/github/ephemient/aoc2024/Day15.kt)|[day15.py](py/aoc2024/day15.py)||
 |[Day16.hs](hs/src/Day16.hs)|[Day16.kt](kt/aoc2024-lib/src/commonMain/kotlin/com/github/ephemient/aoc2024/Day16.kt)|[day16.py](py/aoc2024/day16.py)||
 |[Day17.hs](hs/src/Day17.hs)|[Day17.kt](kt/aoc2024-lib/src/commonMain/kotlin/com/github/ephemient/aoc2024/Day17.kt)|||

rs/benches/criterion.rs

@@ -1,4 +1,6 @@
-use aoc2024::{day1, day10, day11, day12, day13, day2, day3, day4, day5, day6, day7, day8, day9};
+use aoc2024::{
+    day1, day10, day11, day12, day13, day14, day2, day3, day4, day5, day6, day7, day8, day9,
+};
 use criterion::{black_box, Criterion};
 use std::env;
 use std::fs;
@@ -92,6 +94,12 @@ fn aoc2024_bench(c: &mut Criterion) -> io::Result<()> {
     g.bench_function("part 2", |b| b.iter(|| day13::part2(black_box(&data))));
     g.finish();
 
+    let data = get_day_input(14)?;
+    let mut g = c.benchmark_group("day 14");
+    g.bench_function("part 1", |b| b.iter(|| day14::part1(black_box(&data))));
+    g.bench_function("part 2", |b| b.iter(|| day14::part2(black_box(&data))));
+    g.finish();
+
     Ok(())
 }
 

rs/src/day14.rs

@@ -0,0 +1,95 @@
+use std::cmp::Ordering;
+
+use itertools::Itertools;
+
+const WIDTH: isize = 101;
+const HEIGHT: isize = 103;
+
+#[derive(Clone, Copy, Debug)]
+struct Robot {
+    x0: isize,
+    y0: isize,
+    vx: isize,
+    vy: isize,
+}
+
+fn parse(data: &str) -> impl Iterator<Item = Robot> + use<'_> {
+    data.lines().filter_map(|line| {
+        let (p, v) = line.split_once(' ')?;
+        let (x0, y0) = p.strip_prefix("p=")?.split_once(',')?;
+        let (vx, vy) = v.strip_prefix("v=")?.split_once(',')?;
+        Some(Robot {
+            x0: x0.parse().ok()?,
+            y0: y0.parse().ok()?,
+            vx: vx.parse().ok()?,
+            vy: vy.parse().ok()?,
+        })
+    })
+}
+
+pub fn part1(data: &str) -> usize {
+    part1_(data, WIDTH, HEIGHT)
+}
+
+fn part1_(data: &str, width: isize, height: isize) -> usize {
+    let (mut q1, mut q2, mut q3, mut q4) = (0, 0, 0, 0);
+    for Robot { x0, y0, vx, vy } in parse(data) {
+        let x = (x0 + vx * 100).rem_euclid(width);
+        let y = (y0 + vy * 100).rem_euclid(height);
+        match ((width / 2).cmp(&x), (height / 2).cmp(&y)) {
+            (Ordering::Less, Ordering::Less) => q1 += 1,
+            (Ordering::Less, Ordering::Greater) => q2 += 1,
+            (Ordering::Greater, Ordering::Less) => q3 += 1,
+            (Ordering::Greater, Ordering::Greater) => q4 += 1,
+            _ => {}
+        }
+    }
+    q1 * q2 * q3 * q4
+}
+
+pub fn part2(data: &str) -> Option<usize> {
+    let robots = parse(data).collect::<Vec<_>>();
+    (0..WIDTH * HEIGHT)
+        .max_by_key(|t| {
+            robots
+                .iter()
+                .map(|Robot { x0, y0, vx, vy }| {
+                    (
+                        (x0 + vx * t).rem_euclid(WIDTH),
+                        (y0 + vy * t).rem_euclid(HEIGHT),
+                    )
+                })
+                .sorted()
+                .tuple_windows()
+                .filter(|((x, y), next)| (*x, y + 1) == *next)
+                .count()
+        })
+        .and_then(|t| t.try_into().ok())
+}
+
+#[cfg(test)]
+mod tests {
+    use super::*;
+    use indoc::indoc;
+    use pretty_assertions::assert_eq;
+
+    static EXAMPLE: &str = indoc! {"
+        p=0,4 v=3,-3
+        p=6,3 v=-1,-3
+        p=10,3 v=-1,2
+        p=2,0 v=2,-1
+        p=0,0 v=1,3
+        p=3,0 v=-2,-2
+        p=7,6 v=-1,-3
+        p=3,0 v=-1,-2
+        p=9,3 v=2,3
+        p=7,3 v=-1,2
+        p=2,4 v=2,-3
+        p=9,5 v=-3,-3
+    "};
+
+    #[test]
+    fn part1_examples() {
+        assert_eq!(12, part1_(EXAMPLE, 11, 7));
+    }
+}

rs/src/lib.rs

@@ -3,6 +3,7 @@ pub mod day10;
 pub mod day11;
 pub mod day12;
 pub mod day13;
+pub mod day14;
 pub mod day2;
 pub mod day3;
 pub mod day4;

rs/src/main.rs

@@ -1,5 +1,7 @@
 use anyhow::anyhow;
-use aoc2024::{day1, day10, day11, day12, day13, day2, day3, day4, day5, day6, day7, day8, day9};
+use aoc2024::{
+    day1, day10, day11, day12, day13, day14, day2, day3, day4, day5, day6, day7, day8, day9,
+};
 use std::collections::HashSet;
 use std::env;
 use std::fs;
@@ -121,5 +123,13 @@ fn main() -> anyhow::Result<()> {
         println!();
     }
 
+    if args.is_empty() || args.contains("14") {
+        println!("Day 14");
+        let data = get_day_input(14)?;
+        println!("{:?}", day14::part1(&data));
+        println!("{:?}", day14::part2(&data).ok_or(anyhow!("None"))?);
+        println!();
+    }
+
     Ok(())
 }