From 05f9ffa320b4651c24257be84b63b4f6f01fb047 Mon Sep 17 00:00:00 2001
From: Matej Focko <me@mfocko.xyz>
Date: Sat, 7 Jan 2023 20:07:31 +0100
Subject: [PATCH] day(18): refactor a bit

Signed-off-by: Matej Focko <me@mfocko.xyz>
---
 src/bin/day18.rs | 70 ++++++++++++++++++++++++------------------------
 1 file changed, 35 insertions(+), 35 deletions(-)

diff --git a/src/bin/day18.rs b/src/bin/day18.rs
index 4924681..484dc54 100644
--- a/src/bin/day18.rs
+++ b/src/bin/day18.rs
@@ -20,26 +20,20 @@ lazy_static! {
 }
 
 fn get_bounding_box(droplets: &[Coord]) -> (Coord, Coord) {
-    let min_coord =
+    fn find(init: i32, comparator: &dyn Fn(i32, i32) -> i32, droplets: &[Coord]) -> Coord {
         droplets
             .iter()
-            .fold(Coord::new(i32::MAX, i32::MAX, i32::MAX), |acc, &droplet| {
+            .fold(Coord::new(init, init, init), |acc, &droplet| {
                 Coord::new(
-                    min(acc.x(), droplet.x()),
-                    min(acc.y(), droplet.y()),
-                    min(acc.z(), droplet.z()),
+                    comparator(acc.x(), droplet.x()),
+                    comparator(acc.y(), droplet.y()),
+                    comparator(acc.z(), droplet.z()),
                 )
-            });
-    let max_coord =
-        droplets
-            .iter()
-            .fold(Coord::new(i32::MIN, i32::MIN, i32::MIN), |acc, &droplet| {
-                Coord::new(
-                    max(acc.x(), droplet.x()),
-                    max(acc.y(), droplet.y()),
-                    max(acc.z(), droplet.z()),
-                )
-            });
+            })
+    }
+
+    let min_coord = find(i32::MAX, &min, droplets);
+    let max_coord = find(i32::MIN, &max, droplets);
 
     (min_coord, max_coord)
 }
@@ -63,6 +57,30 @@ enum Cube {
     Obsidian,
 }
 
+fn construct_space(min_coords: Coord, max_coords: Coord) -> BTreeMap<Coord, Cube> {
+    let mut space = BTreeMap::<Coord, Cube>::new();
+
+    for cube in [
+        min_coords.x()..=max_coords.x(),
+        min_coords.y()..=max_coords.y(),
+        min_coords.z()..=max_coords.z(),
+    ]
+    .into_iter()
+    .multi_cartesian_product()
+    .map(|coords| {
+        let (x, y, z) = coords
+            .into_iter()
+            .collect_tuple::<(i32, i32, i32)>()
+            .unwrap();
+
+        Coord::new(x, y, z)
+    }) {
+        space.insert(cube, Cube::Lava);
+    }
+
+    space
+}
+
 fn aerate(space: &mut BTreeMap<Coord, Cube>, start: Coord) {
     let mut queue = VecDeque::<Coord>::new();
     queue.push_back(start);
@@ -116,29 +134,11 @@ impl Solution<Input, Output> for Day18 {
     }
 
     fn part_2(input: &Input) -> Output {
-        let mut space = BTreeMap::<Coord, Cube>::new();
-
         _check_bounding_box(input); // for debugging purposes
         let (min_coords, max_coords) = get_bounding_box(input);
 
         // lava everywhere
-        for cube in [
-            min_coords.x()..=max_coords.x(),
-            min_coords.y()..=max_coords.y(),
-            min_coords.z()..=max_coords.z(),
-        ]
-        .into_iter()
-        .multi_cartesian_product()
-        .map(|coords| {
-            let (x, y, z) = coords
-                .into_iter()
-                .collect_tuple::<(i32, i32, i32)>()
-                .unwrap();
-
-            Coord::new(x, y, z)
-        }) {
-            space.insert(cube, Cube::Lava);
-        }
+        let mut space = construct_space(min_coords, max_coords);
 
         // override with obsidian
         for &droplet in input {