2025 Day 8 (dirty)

Author: hsaikia

src/bin/2025_08/main.rs

@@ -0,0 +1,122 @@
+use std::collections::HashMap;
+
+use aoc::{
+    common::{self, HashMapCount},
+    io,
+};
+use itertools::Itertools;
+
+struct Box {
+    pub x: usize,
+    y: usize,
+    z: usize,
+}
+
+impl Box {
+    fn new(x: usize, y: usize, z: usize) -> Self {
+        Self { x, y, z }
+    }
+
+    fn dist(b1: &Box, b2: &Box) -> usize {
+        let dx = b1.x.abs_diff(b2.x);
+        let dy = b1.y.abs_diff(b2.y);
+        let dz = b1.z.abs_diff(b2.z);
+        dx * dx + dy * dy + dz * dz
+    }
+}
+
+fn find_group(gm: &HashMap<usize, usize>, g: usize) -> usize {
+    let mut ret = g;
+    while let Some(i) = gm.get(&ret) {
+        ret = *i;
+    }
+    ret
+}
+
+fn all_connected(gm: &HashMap<usize, usize>, groups: usize) -> bool {
+    (0..groups).all(|g| find_group(gm, g) == 0)
+}
+
+fn solve<const PART: usize, const MIN_CONNECTIONS: usize>(input: &str) -> usize {
+    let mut boxes = Vec::new();
+    for line in input.lines() {
+        if line.is_empty() {
+            continue;
+        }
+        let coords: Vec<usize> = io::tokenize_nums(line, ",");
+        boxes.push(Box::new(coords[0], coords[1], coords[2]));
+    }
+
+    let mut distances = Vec::new();
+    for i in 0..boxes.len() {
+        for j in i + 1..boxes.len() {
+            distances.push((i, j, Box::dist(&boxes[i], &boxes[j])));
+        }
+    }
+
+    distances.sort_by(|a, b| a.2.cmp(&b.2));
+
+    let mut group_mapping: HashMap<usize, usize> = HashMap::new();
+
+    for (i, j, _) in distances.iter().take(if PART == 1 {
+        MIN_CONNECTIONS
+    } else {
+        distances.len()
+    }) {
+        let g1 = find_group(&group_mapping, *i);
+        let g2 = find_group(&group_mapping, *j);
+
+        //println!("Joining {} and {} | groups {} and {}", i, j, g1, g2);
+        if g1 == g2 {
+            continue;
+        }
+
+        let g = g1.min(g2);
+
+        if g1 != g {
+            group_mapping.insert(g1, g);
+        }
+        if g2 != g {
+            group_mapping.insert(g2, g);
+        }
+
+        if all_connected(&group_mapping, boxes.len()) {
+            return boxes[*i].x * boxes[*j].x;
+        }
+    }
+
+    let mut group_to_member_count: HashMap<usize, usize> = HashMap::new();
+
+    for i in 0..boxes.len() {
+        let g = find_group(&group_mapping, i);
+        //println!("Box {} belongs to group {}", i, g);
+        group_to_member_count.insert_with_count(&g, 1);
+    }
+
+    //dbg!(&group_to_member_count);
+
+    group_to_member_count
+        .values()
+        .sorted_by(|a, b| b.cmp(a))
+        .take(3)
+        .product()
+}
+
+fn main() {
+    if let Some(input) = common::get_input() {
+        common::timed(&input, solve::<1, 1000>, true);
+        common::timed(&input, solve::<2, 1000>, false);
+    }
+}
+
+#[cfg(test)]
+mod tests {
+    use super::*;
+
+    #[test]
+    fn test_samples() {
+        let sample_input = "162,817,812\n57,618,57\n906,360,560\n592,479,940\n352,342,300\n466,668,158\n542,29,236\n431,825,988\n739,650,466\n52,470,668\n216,146,977\n819,987,18\n117,168,530\n805,96,715\n346,949,466\n970,615,88\n941,993,340\n862,61,35\n984,92,344\n425,690,689";
+        assert_eq!(solve::<1, 10>(sample_input), 40);
+        assert_eq!(solve::<2, 10>(sample_input), 25272);
+    }
+}