[2023] Complete day 18

README.md

@@ -22,6 +22,7 @@ Thank you to [Eric Wastl](http://was.tl) for running this incredible yearly even
 - [Day 15: Lens Library](aoc_2023/src/day_15.rs)
 - [Day 16: The Floor Will Be Lava](aoc_2023/src/day_16.rs)
 - [Day 17: Clumsy Crucible](aoc_2023/src/day_17.rs)
+- [Day 18: Lavaduct Lagoon](aoc_2023/src/day_18.rs)
 <!-- MARKER -->
 
 ## [2022](https://adventofcode.com/2022) [![aoc_2022](https://github.com/Basicprogrammer10/advent-of-code/actions/workflows/aoc_2022.yml/badge.svg)](https://github.com/Basicprogrammer10/advent-of-code/actions/workflows/aoc_2022.yml)

aoc_2023/src/aoc_lib/direction.rs

@@ -1,5 +1,5 @@
 use nd_vec::{vector, Vec2};
-use num_traits::Num;
+use num_traits::{Num, Signed};
 
 #[derive(Debug, Clone, Copy, PartialEq, Eq, Hash)]
 pub enum Direction {
@@ -18,6 +18,15 @@ impl Direction {
         Direction::Right,
     ];
 
+    pub fn as_vector<T: Num + Signed + Copy>(&self) -> Vec2<T> {
+        match self {
+            Self::Up => vector!(T::zero(), -T::one()),
+            Self::Down => vector!(T::zero(), T::one()),
+            Self::Left => vector!(-T::one(), T::zero()),
+            Self::Right => vector!(T::one(), T::zero()),
+        }
+    }
+
     #[rustfmt::skip]
     pub fn try_advance<T: Num + Copy + PartialOrd>(&self, pos: Vec2<T>) -> Option<Vec2<T>> {
         Some(match self {

aoc_2023/src/day_18.rs

@@ -0,0 +1,108 @@
+use common::{Answer, Solution};
+use nd_vec::vector;
+
+use crate::aoc_lib::direction::Direction;
+
+pub struct Day18;
+
+impl Solution for Day18 {
+    fn name(&self) -> &'static str {
+        "Lavaduct Lagoon"
+    }
+
+    fn part_a(&self, input: &str) -> Answer {
+        solve(&parse_a(input)).into()
+    }
+
+    fn part_b(&self, input: &str) -> Answer {
+        solve(&parse_b(input)).into()
+    }
+}
+
+fn solve(instructions: &[(Direction, u32)]) -> i64 {
+    let mut pos = vector!(0, 0);
+    let mut perimeter = 0;
+    let mut area = 0;
+
+    for (dir, steps) in instructions.iter().copied() {
+        let dir = dir.as_vector();
+        let cng = dir * (steps as i64);
+        pos += cng;
+
+        perimeter += steps as i64;
+        area += pos.x() * cng.y();
+    }
+
+    area + perimeter / 2 + 1
+}
+
+fn parse_b(input: &str) -> Vec<(Direction, u32)> {
+    input
+        .lines()
+        .map(|line| {
+            let hex = &line[line.find('#').unwrap() + 1..line.len() - 1];
+            let steps = u32::from_str_radix(&hex[0..5], 16).unwrap();
+            let dir = match &hex[5..6] {
+                "0" => Direction::Right,
+                "1" => Direction::Down,
+                "2" => Direction::Left,
+                "3" => Direction::Up,
+                _ => panic!("Invalid direction"),
+            };
+            (dir, steps)
+        })
+        .collect()
+}
+
+fn parse_a(input: &str) -> Vec<(Direction, u32)> {
+    input
+        .lines()
+        .map(|line| {
+            let mut parts = line.split_whitespace();
+            let dir = match parts.next().unwrap() {
+                "R" => Direction::Right,
+                "L" => Direction::Left,
+                "U" => Direction::Up,
+                "D" => Direction::Down,
+                _ => panic!("Invalid direction"),
+            };
+            let steps = parts.next().unwrap();
+            (dir, steps.parse().unwrap())
+        })
+        .collect()
+}
+
+#[cfg(test)]
+mod test {
+    use common::Solution;
+    use indoc::indoc;
+
+    use super::Day18;
+
+    const CASE: &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 part_a() {
+        assert_eq!(Day18.part_a(CASE), 62.into());
+    }
+
+    #[test]
+    fn part_b() {
+        assert_eq!(Day18.part_b(CASE), 952408144115i64.into());
+    }
+}

aoc_2023/src/lib.rs

@@ -19,6 +19,7 @@ mod day_14;
 mod day_15;
 mod day_16;
 mod day_17;
+mod day_18;
 // [import_marker]
 
 #[rustfmt::skip]
@@ -40,5 +41,6 @@ pub const ALL: &[&dyn Solution] = &[
     &day_15::Day15,
     &day_16::Day16,
     &day_17::Day17,
+    &day_18::Day18,
     // [list_marker]
 ];