2022 day 18

2022/rust/src/solutions/day18.rs

@@ -1,3 +1,4 @@
+#![allow(dead_code)]
 use std::collections::HashSet;
 use crate::utils;
 
@@ -14,18 +15,16 @@ pub fn run() -> () {
 type Point = (isize, isize, isize);
 
 
+fn sides_for((x, y, z): Point) -> impl Iterator<Item=Point> {
+    [(x - 1, y, z), (x + 1, y, z), (x, y - 1, z), (x, y + 1, z), (x, y, z - 1), (x, y, z + 1)].into_iter()
+}
+
 fn solve1(data: &[Point]) -> i32 {
     let points: HashSet<Point> = HashSet::from_iter(data.iter().copied());
 
     let mut side_sum = 0;
-    for &(p_x, p_y, p_z) in data {
-        let sides = [
-            (p_x - 1, p_y, p_z), (p_x + 1, p_y, p_z),
-            (p_x, p_y - 1, p_z), (p_x, p_y + 1, p_z),
-            (p_x, p_y, p_z - 1), (p_x, p_y, p_z + 1),
-        ];
-
-        for side in sides {
+    for &point in data {
+        for side in sides_for(point) {
             if !points.contains(&side) {
                 side_sum += 1;
             }
@@ -35,7 +34,33 @@ fn solve1(data: &[Point]) -> i32 {
 }
 
 fn solve2(data: &[Point]) -> i32 {
-    2
+    let points: HashSet<Point> = HashSet::from_iter(data.iter().copied());
+    let (x_min, y_min, z_min) = data.iter().copied().reduce(|(x1, y1, z1), (x2, y2, z2)| (x1.min(x2), y1.min(y2), z1.min(z2))).unwrap();
+    let (x_max, y_max, z_max) = data.iter().copied().reduce(|(x1, y1, z1), (x2, y2, z2)| (x1.max(x2), y1.max(y2), z1.max(z2))).unwrap();
+
+    let (x_min, y_min, z_min) = (x_min - 1, y_min - 1, z_min - 1);
+    let (x_max, y_max, z_max) = (x_max + 1, y_max + 1, z_max + 1);
+
+    let fits = move |&(x, y, z): &Point| {
+        x_min <= x && x <= x_max && y_min <= y && y <= y_max && z_min <= z && z <= z_max
+    };
+
+    let mut to_check: Vec<Point> = vec![(x_min, y_min, z_min)];
+    let mut visited: HashSet<Point> = HashSet::new();
+    let mut side_sum = 0;
+    while let Some(current) = to_check.pop() {
+        match visited.contains(&current) {
+            true => continue,
+            false => visited.insert(current),
+        };
+        for neighbour in sides_for(current).filter(fits) {
+            match points.contains(&neighbour) {
+                true => side_sum += 1,
+                false => to_check.push(neighbour),
+            }
+        }
+    }
+    side_sum
 }
 
 
@@ -69,6 +94,6 @@ mod tests {
 
     #[test]
     fn part2() {
-        assert_eq!(2, solve2(&parse_data(DATA)));
+        assert_eq!(58, solve2(&parse_data(DATA)));
     }
 }