day18 part1

1 files changed, 72 insertions, 0 deletions

diff --git a/src/bin/day18.rs b/src/bin/day18.rs
new file mode 100644
index 0000000..87f2133
--- /dev/null
+++ b/src/bin/day18.rs
@@ -0,0 +1,72 @@
+static DAY: u8 = 18;
+
+fn main() {
+    let input = advent::read_lines(DAY);
+    println!("{DAY}a: {}", surface_area(&input));
+    println!("{DAY}b: {}", 0);
+}
+
+struct Cube {
+    x: i32,
+    y: i32,
+    z: i32,
+}
+
+impl Cube {
+    fn new(input: &str) -> Cube {
+        let mut coords = input.split(',');
+        let x = coords.next().unwrap().parse().unwrap();
+        let y = coords.next().unwrap().parse().unwrap();
+        let z = coords.next().unwrap().parse().unwrap();
+        Cube { x, y, z }
+    }
+
+    fn unconnected_surfaces(&self, cubes: &[Cube]) -> usize {
+        let neighbors = [
+            (self.x + 1, self.y, self.z),
+            (self.x - 1, self.y, self.z),
+            (self.x, self.y + 1, self.z),
+            (self.x, self.y - 1, self.z),
+            (self.x, self.y, self.z + 1),
+            (self.x, self.y, self.z - 1),
+        ];
+        6 - cubes.iter()
+             .filter(|c| neighbors.contains(&(c.x, c.y, c.z)))
+             .count()
+    }
+}
+
+fn surface_area(input: &[String]) -> usize {
+    let cubes = input.iter()
+                     .map(|x| Cube::new(x))
+                     .collect::<Vec<_>>();
+    cubes.iter()
+         .map(|c| c.unconnected_surfaces(&cubes))
+         .sum()
+}
+
+#[cfg(test)]
+mod tests {
+    use super::*;
+
+    #[test]
+    fn test() {
+        let input = [
+            "2,2,2",
+            "1,2,2",
+            "3,2,2",
+            "2,1,2",
+            "2,3,2",
+            "2,2,1",
+            "2,2,3",
+            "2,2,4",
+            "2,2,6",
+            "1,2,5",
+            "3,2,5",
+            "2,1,5",
+            "2,3,5",
+        ].iter().map(|&x| String::from(x)).collect::<Vec<_>>();
+
+        assert_eq!(surface_area(&input), 64);
+    }
+}