Day 18: Lavaduct Lagoon

ephemient · Dec 18, 2023 · f2705f7 · f2705f7
1 parent 4993a07
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diff --git a/README.md b/README.md
@@ -22,4 +22,4 @@ Development occurs in language-specific directories:
 |[Day15.hs](hs/src/Day15.hs)|[Day15.kt](kt/aoc2023-lib/src/commonMain/kotlin/com/github/ephemient/aoc2023/Day15.kt)|[day15.py](py/aoc2023/day15.py)|[day15.rs](rs/src/day15.rs)|
 |[Day16.hs](hs/src/Day16.hs)|[Day16.kt](kt/aoc2023-lib/src/commonMain/kotlin/com/github/ephemient/aoc2023/Day16.kt)|[day16.py](py/aoc2023/day16.py)|[day16.rs](rs/src/day16.rs)|
 |[Day17.hs](hs/src/Day17.hs)|[Day17.kt](kt/aoc2023-lib/src/commonMain/kotlin/com/github/ephemient/aoc2023/Day17.kt)|[day17.py](py/aoc2023/day17.py)|[day17.rs](rs/src/day17.rs)|
-|[Day18.hs](hs/src/Day18.hs)|[Day18.kt](kt/aoc2023-lib/src/commonMain/kotlin/com/github/ephemient/aoc2023/Day18.kt)|[day18.py](py/aoc2023/day18.py)||
+|[Day18.hs](hs/src/Day18.hs)|[Day18.kt](kt/aoc2023-lib/src/commonMain/kotlin/com/github/ephemient/aoc2023/Day18.kt)|[day18.py](py/aoc2023/day18.py)|[day18.rs](rs/src/day18.rs)|
diff --git a/rs/benches/criterion.rs b/rs/benches/criterion.rs
@@ -1,6 +1,6 @@
 use aoc2023::{
-    day1, day10, day11, day12, day13, day14, day15, day16, day17, day2, day3, day4, day5, day6,
-    day7, day8, day9,
+    day1, day10, day11, day12, day13, day14, day15, day16, day17, day18, day2, day3, day4, day5,
+    day6, day7, day8, day9,
 };
 use criterion::{black_box, Criterion};
 use std::env;
@@ -119,6 +119,12 @@ fn aoc2023_bench(c: &mut Criterion) -> io::Result<()> {
     g.bench_function("part 2", |b| b.iter(|| day17::part2(black_box(&data))));
     g.finish();
 
+    let data = get_day_input(18)?;
+    let mut g = c.benchmark_group("day 18");
+    g.bench_function("part 1", |b| b.iter(|| day18::part1(black_box(&data))));
+    g.bench_function("part 2", |b| b.iter(|| day18::part2(black_box(&data))));
+    g.finish();
+
     Ok(())
 }
 

diff --git a/rs/src/day18.rs b/rs/src/day18.rs
@@ -0,0 +1,104 @@
+enum Direction {
+    R,
+    D,
+    L,
+    U,
+}
+
+fn solve<I: IntoIterator<Item = (Direction, u32)>>(data: I) -> u64 {
+    let (mut x, mut y, mut a, mut l) = (0, 0, 0, 0);
+    for (d, n) in data {
+        match d {
+            Direction::R => {
+                x += i64::from(n);
+                a += y * i64::from(n);
+            }
+            Direction::D => {
+                y += i64::from(n);
+            }
+            Direction::L => {
+                x -= i64::from(n);
+                a -= y * i64::from(n);
+            }
+            Direction::U => {
+                y -= i64::from(n);
+            }
+        }
+        l += u64::from(n);
+    }
+    debug_assert_eq!((x, y), (0, 0));
+    a.unsigned_abs() + l / 2 + 1
+}
+
+pub fn part1(data: &str) -> u64 {
+    solve(data.lines().filter_map(|line| {
+        let mut iter = line.split(' ');
+        let d = iter.next()?;
+        let d = if d == "R" {
+            Direction::R
+        } else if d == "D" {
+            Direction::D
+        } else if d == "L" {
+            Direction::L
+        } else if d == "U" {
+            Direction::U
+        } else {
+            return None;
+        };
+        Some((d, iter.next()?.parse::<u32>().ok()?))
+    }))
+}
+
+pub fn part2(data: &str) -> u64 {
+    solve(data.lines().filter_map(|line| {
+        let line = line
+            .split(' ')
+            .next_back()?
+            .strip_prefix("(#")?
+            .strip_suffix(')')?;
+        let d = match line.bytes().last()? {
+            b'0' => Direction::R,
+            b'1' => Direction::D,
+            b'2' => Direction::L,
+            b'3' => Direction::U,
+            _ => {
+                return None;
+            }
+        };
+        Some((d, u32::from_str_radix(&line[..line.len() - 1], 16).ok()?))
+    }))
+}
+
+#[cfg(test)]
+mod tests {
+    use super::*;
+    use indoc::indoc;
+    use pretty_assertions::assert_eq;
+
+    static EXAMPLE: &str = indoc! {"
+        R 6 (#70c710)
+        D 5 (#0dc571)
+        L 2 (#5713f0)
+        D 2 (#d2c081)
+        R 2 (#59c680)
+        D 2 (#411b91)
+        L 5 (#8ceee2)
+        U 2 (#caa173)
+        L 1 (#1b58a2)
+        U 2 (#caa171)
+        R 2 (#7807d2)
+        U 3 (#a77fa3)
+        L 2 (#015232)
+        U 2 (#7a21e3)
+    "};
+
+    #[test]
+    fn part1_examples() {
+        assert_eq!(62, part1(EXAMPLE));
+    }
+
+    #[test]
+    fn part2_examples() {
+        assert_eq!(952408144115, part2(EXAMPLE));
+    }
+}
diff --git a/rs/src/lib.rs b/rs/src/lib.rs
@@ -7,6 +7,7 @@ pub mod day14;
 pub mod day15;
 pub mod day16;
 pub mod day17;
+pub mod day18;
 pub mod day2;
 pub mod day3;
 pub mod day4;

diff --git a/rs/src/main.rs b/rs/src/main.rs
@@ -1,6 +1,6 @@
 use aoc2023::{
-    day1, day10, day11, day12, day13, day14, day15, day16, day17, day2, day3, day4, day5, day6,
-    day7, day8, day9,
+    day1, day10, day11, day12, day13, day14, day15, day16, day17, day18, day2, day3, day4, day5,
+    day6, day7, day8, day9,
 };
 use std::collections::HashSet;
 use std::env;
@@ -155,5 +155,13 @@ fn main() -> io::Result<()> {
         println!();
     }
 
+    if args.is_empty() || args.contains("18") {
+        println!("Day 18");
+        let data = get_day_input(18)?;
+        println!("{:?}", day18::part1(&data));
+        println!("{:?}", day18::part2(&data));
+        println!();
+    }
+
     Ok(())
 }