AoC 2025 Day 8 - rust

Author: pareronia

README.md

@@ -13,7 +13,7 @@
 | python3 | [✓](src/main/python/AoC2025_01.py) | [✓](src/main/python/AoC2025_02.py) | [✓](src/main/python/AoC2025_03.py) | [✓](src/main/python/AoC2025_04.py) | [✓](src/main/python/AoC2025_05.py) | [✓](src/main/python/AoC2025_06.py) | [✓](src/main/python/AoC2025_07.py) | [✓](src/main/python/AoC2025_08.py) | [✓](src/main/python/AoC2025_09.py) | [✓](src/main/python/AoC2025_10.py) | [✓](src/main/python/AoC2025_11.py) | [✓](src/main/python/AoC2025_12.py) |
 | java | [✓](src/main/java/AoC2025_01.java) | [✓](src/main/java/AoC2025_02.java) | [✓](src/main/java/AoC2025_03.java) | [✓](src/main/java/AoC2025_04.java) | [✓](src/main/java/AoC2025_05.java) | [✓](src/main/java/AoC2025_06.java) | [✓](src/main/java/AoC2025_07.java) | [✓](src/main/java/AoC2025_08.java) | [✓](src/main/java/AoC2025_09.java) | [✓](src/main/java/AoC2025_10.java) | [✓](src/main/java/AoC2025_11.java) | [✓](src/main/java/AoC2025_12.java) |
 | bash | [✓](src/main/bash/AoC2025_01.sh) | [✓](src/main/bash/AoC2025_02.sh) | [✓](src/main/bash/AoC2025_03.sh) | [✓](src/main/bash/AoC2025_04.sh) | [✓](src/main/bash/AoC2025_05.sh) | [✓](src/main/bash/AoC2025_06.sh) | [✓](src/main/bash/AoC2025_07.sh) | | | | [✓](src/main/bash/AoC2025_11.sh) | [✓](src/main/bash/AoC2025_12.sh) |
-| rust | [✓](src/main/rust/AoC2025_01/src/main.rs) | [✓](src/main/rust/AoC2025_02/src/main.rs) | [✓](src/main/rust/AoC2025_03/src/main.rs) | [✓](src/main/rust/AoC2025_04/src/main.rs) | [✓](src/main/rust/AoC2025_05/src/main.rs) | [✓](src/main/rust/AoC2025_06/src/main.rs) | [✓](src/main/rust/AoC2025_07/src/main.rs) | | | | | |
+| rust | [✓](src/main/rust/AoC2025_01/src/main.rs) | [✓](src/main/rust/AoC2025_02/src/main.rs) | [✓](src/main/rust/AoC2025_03/src/main.rs) | [✓](src/main/rust/AoC2025_04/src/main.rs) | [✓](src/main/rust/AoC2025_05/src/main.rs) | [✓](src/main/rust/AoC2025_06/src/main.rs) | [✓](src/main/rust/AoC2025_07/src/main.rs) | [✓](src/main/rust/AoC2025_08/src/main.rs) | | | | |
 <!-- @END:ImplementationsTable:2025@ -->
 
 ## 2024

src/main/rust/AoC2025_08/Cargo.toml

@@ -0,0 +1,8 @@
+[package]
+name = "AoC2025_08"
+version = "0.1.0"
+edition = "2021"
+
+[dependencies]
+aoc = { path = "../aoc" }
+itertools = "0.11"

src/main/rust/AoC2025_08/src/main.rs

@@ -0,0 +1,179 @@
+#![allow(non_snake_case)]
+
+use aoc::geometry3d::XYZ;
+use aoc::Puzzle;
+use itertools::Itertools;
+
+#[derive(Clone)]
+struct Box {
+ idx: usize,
+ position: XYZ,
+}
+
+struct Pair {
+ first: Box,
+ second: Box,
+ distance: u64,
+}
+
+struct UnionFind {
+ sz: Vec<usize>,
+ ids: Vec<usize>,
+ components: usize,
+}
+
+impl UnionFind {
+ fn new(size: usize) -> Self {
+ UnionFind {
+ sz: vec![1; size],
+ ids: (0..size).collect::<Vec<_>>(),
+ components: size,
+ }
+ }
+
+ fn find(&self, p: usize) -> usize {
+ let mut root = p;
+ while root != self.ids[root] {
+ root = self.ids[root];
+ }
+ root
+ }
+
+ fn unify(&mut self, p: usize, q: usize) {
+ let root_p = self.find(p);
+ let root_q = self.find(q);
+ if root_p != root_q {
+ if self.sz[root_p] < self.sz[root_q] {
+ self.sz[root_q] += self.sz[root_p];
+ self.ids[root_p] = root_q;
+ self.sz[root_p] = 0;
+ } else {
+ self.sz[root_p] += self.sz[root_q];
+ self.ids[root_q] = root_p;
+ self.sz[root_q] = 0;
+ }
+ self.components -= 1;
+ }
+ }
+}
+
+struct AoC2025_08;
+
+impl AoC2025_08 {
+ fn solve_1(
+ &self,
+ num_boxes: usize,
+ pairs: &[Pair],
+ size: usize,
+ ) -> <Self as Puzzle>::Output1 {
+ let mut dsu = UnionFind::new(num_boxes);
+ pairs
+ .iter()
+ .take(size)
+ .for_each(|pair| dsu.unify(pair.first.idx, pair.second.idx));
+ dsu.sz.iter().sorted().rev().take(3).product()
+ }
+
+ fn sample_part_1(
+ &self,
+ input: &<Self as Puzzle>::Input,
+ ) -> <Self as Puzzle>::Output1 {
+ self.solve_1(input.0, &input.1, 10)
+ }
+}
+
+impl aoc::Puzzle for AoC2025_08 {
+ type Input = (usize, Vec<Pair>);
+ type Output1 = usize;
+ type Output2 = u64;
+
+ aoc::puzzle_year_day!(2025, 8);
+
+ fn parse_input(&self, lines: Vec<String>) -> Self::Input {
+ let boxes = lines
+ .iter()
+ .enumerate()
+ .map(|(idx, line)| Box {
+ idx,
+ position: XYZ::from_iter(
+ line.split(',').map(|sp| sp.parse::<u32>().unwrap()),
+ ),
+ })
+ .collect::<Vec<_>>();
+ let pairs = boxes
+ .iter()
+ .enumerate()
+ .flat_map(|(i, r#box)| {
+ (i + 1..boxes.len()).map(|j| Pair {
+ first: r#box.clone(),
+ second: boxes[j].clone(),
+ distance: r#box
+ .position
+ .squared_distance(&boxes[j].position),
+ })
+ })
+ .sorted_by(|p1, p2| Ord::cmp(&p1.distance, &p2.distance))
+ .collect::<Vec<_>>();
+ (boxes.len(), pairs)
+ }
+
+ fn part_1(&self, input: &Self::Input) -> Self::Output1 {
+ self.solve_1(input.0, &input.1, 1000)
+ }
+
+ fn part_2(&self, input: &Self::Input) -> Self::Output2 {
+ let mut dsu = UnionFind::new(input.0);
+ for pair in input.1.iter() {
+ dsu.unify(pair.first.idx, pair.second.idx);
+ if dsu.components == 1 && dsu.sz[dsu.find(0)] == input.0 {
+ return pair.first.position.x() as u64
+ * pair.second.position.x() as u64;
+ }
+ }
+ unreachable!();
+ }
+
+ fn samples(&self) {
+ aoc::puzzle_samples! {
+ self, sample_part_1, TEST, 40,
+ self, part_2, TEST, 25272
+ };
+ }
+}
+
+fn main() {
+ AoC2025_08 {}.run(std::env::args());
+}
+
+const TEST: &str = "\
+162,817,812
+57,618,57
+906,360,560
+592,479,940
+352,342,300
+466,668,158
+542,29,236
+431,825,988
+739,650,466
+52,470,668
+216,146,977
+819,987,18
+117,168,530
+805,96,715
+346,949,466
+970,615,88
+941,993,340
+862,61,35
+984,92,344
+425,690,689
+";
+
+#[cfg(test)]
+mod tests {
+ use super::*;
+
+ #[test]
+ pub fn samples() {
+ AoC2025_08 {}.samples();
+ }
+}

src/main/rust/Cargo.lock

@@ -39,6 +39,12 @@ impl XYZ {
  .map(|h| XYZ::try_from(h).unwrap())
  .map(|xyz| self.translate(&xyz, 1))
  }
+
+ pub fn squared_distance(&self, other: &XYZ) -> u64 {
+ ((self.x - other.x) as i64 * (self.x - other.x) as i64) as u64
+ + ((self.y - other.y) as i64 * (self.y - other.y) as i64) as u64
+ + ((self.z - other.z) as i64 * (self.z - other.z) as i64) as u64
+ }
 }
 
 impl FromIterator<u32> for XYZ {