From 6031a9f16ee43d849f47cba93ed36d6fe8276bb7 Mon Sep 17 00:00:00 2001
From: Jeremy Kaplan <jdkaplan@metagram.net>
Date: Sat, 17 Dec 2022 21:14:50 -0800
Subject: [PATCH] 2022 Day 18 Part 1

---
 2022/src/bin/day18.rs | 50 +++++++++++++++++++++++++++++++++++++++++++
 1 file changed, 50 insertions(+)
 create mode 100644 2022/src/bin/day18.rs

diff --git a/2022/src/bin/day18.rs b/2022/src/bin/day18.rs
new file mode 100644
index 0000000..1a34fee
--- /dev/null
+++ b/2022/src/bin/day18.rs
@@ -0,0 +1,50 @@
+const INPUT: &str = include_str!("../../input/day18.txt");
+
+fn main() {
+    println!("{}", part1(INPUT));
+}
+
+fn part1(input: &str) -> usize {
+    let cubes: Vec<Cube> = aoc::lines(input)
+        .map(|line| {
+            let coords: Vec<&str> = line.split(',').collect();
+            let x = coords[0].parse().unwrap();
+            let y = coords[1].parse().unwrap();
+            let z = coords[2].parse().unwrap();
+            Cube::new(x, y, z)
+        })
+        .collect();
+
+    let mut shared_faces = 0;
+    for (c1, c2) in itertools::iproduct!(&cubes, &cubes) {
+        if c1 == c2 {
+            continue;
+        }
+
+        if c1.touches(c2) {
+            shared_faces += 1;
+        }
+    }
+
+    6 * cubes.len() - shared_faces
+}
+
+#[derive(Debug, Copy, Clone, PartialEq, Eq)]
+struct Cube {
+    x: u32,
+    y: u32,
+    z: u32,
+}
+
+impl Cube {
+    fn new(x: u32, y: u32, z: u32) -> Self {
+        Self { x, y, z }
+    }
+
+    fn touches(&self, other: &Self) -> bool {
+        let dx = (self.x as i32 - other.x as i32).abs();
+        let dy = (self.y as i32 - other.y as i32).abs();
+        let dz = (self.z as i32 - other.z as i32).abs();
+        (dx + dy + dz) == 1
+    }
+}