From dee3f6dfbcfc69a671128bd46f507afdf95c30d7 Mon Sep 17 00:00:00 2001
From: Devon Sawatsky <devon@nove.dev>
Date: Mon, 8 Dec 2025 06:20:03 +0000
Subject: [PATCH] day8 part2

---
 src/day8.rs | 60 +++++++++++++++++++++++++++++++++++++++--------------
 src/lib.rs  | 14 ++++++-------
 2 files changed, 51 insertions(+), 23 deletions(-)

diff --git a/src/day8.rs b/src/day8.rs
index 200a649..55a47b4 100644
--- a/src/day8.rs
+++ b/src/day8.rs
@@ -3,23 +3,11 @@ use itertools::Itertools;
 use crate::{spatial::Point3D, union_find::UnionFind};
 
 pub fn day8_part1(input: &str, connection_limit: usize) -> String {
-    let boxes = parse(input);
-    let mut pairs = boxes
-        .iter()
-        .combinations(2)
-        .map(|pair| (pair[0], pair[1]))
-        .map(|(left, right)| (left.euclidean_distance(right), left, right))
-        .collect_vec();
-    pairs.sort_by(|(ld, _, _), (rd, _, _)| ld.partial_cmp(rd).unwrap());
-    let distanceless_pairs = pairs
-        .into_iter()
-        .map(|(_, l, r)| (l, r))
-        .take(connection_limit)
-        .collect_vec();
+    let (box_count, distanceless_pairs) = get_pairs(input, connection_limit);
 
     let mut ufo = UnionFind::default();
 
-    for (&l, &r) in distanceless_pairs {
+    for (l, r) in distanceless_pairs {
         let l = ufo.make_set(l);
         let r = ufo.make_set(r);
         ufo.union(l, r);
@@ -30,8 +18,48 @@ pub fn day8_part1(input: &str, connection_limit: usize) -> String {
     let product = rss.pop().unwrap() * rss.pop().unwrap() * rss.pop().unwrap();
     product.to_string()
 }
-pub fn day8_part2(input: &str) -> String {
-    todo!()
+pub fn day8_part2(input: &str, connection_limit: usize) -> String {
+    let (box_count, distanceless_pairs) = get_pairs(input, connection_limit);
+    println!("{}", distanceless_pairs.len());
+    let mut ufo = UnionFind::default();
+    let mut index = 0;
+
+    let (l, r) = loop {
+        let (l, r) = distanceless_pairs[index];
+
+        let lindex = ufo.make_set(l);
+        let rindex = ufo.make_set(r);
+        ufo.union(lindex, rindex);
+
+        let rss = ufo.root_sizes();
+        println!("{:?}", rss);
+        if rss.len() > 1 || rss[0] < box_count {
+            index += 1;
+        } else {
+            break dbg!((l, r));
+        }
+    };
+    let product = l.x * r.x;
+    product.to_string()
+}
+
+fn get_pairs(input: &str, connection_limit: usize) -> (usize, Vec<(Point3D, Point3D)>) {
+    let boxes = parse(input);
+    let mut pairs = boxes
+        .iter()
+        .combinations(2)
+        .map(|pair| (pair[0], pair[1]))
+        .map(|(left, right)| (left.euclidean_distance(right), left, right))
+        .collect_vec();
+    pairs.sort_by(|(ld, _, _), (rd, _, _)| ld.partial_cmp(rd).unwrap());
+    (
+        boxes.len(),
+        pairs
+            .into_iter()
+            .map(|(_, l, r)| (*l, *r))
+            .take(connection_limit)
+            .collect_vec(),
+    )
 }
 
 fn parse(input: &str) -> Vec<Point3D> {
diff --git a/src/lib.rs b/src/lib.rs
index 69cc8e1..f35844c 100644
--- a/src/lib.rs
+++ b/src/lib.rs
@@ -135,13 +135,13 @@ mod tests {
         let result = day8::day8_part1(include_str!("../input/day8.txt"), 1000);
         assert_eq!(result, "90036");
     }
-    // #[test]
-    // fn day8_part2_test() {
-    //     let test_result = day8::day8_part2(include_str!("../input/day8.test.txt"));
-    //     assert_eq!(test_result, "40");
-    //     // let result = day8::day8_part2(include_str!("../input/day8.txt"));
-    //     // assert_eq!(result, "3806264447357");
-    // }
+    #[test]
+    fn day8_part2_test() {
+        let test_result = day8::day8_part2(include_str!("../input/day8.test.txt"), 1_000_000);
+        assert_eq!(test_result, "25272");
+        let result = day8::day8_part2(include_str!("../input/day8.txt"), 1_000_000);
+        assert_eq!(result, "6083499488");
+    }
 
     #[test]
     fn day7_part1_test() {
-- 
2.51.2