From: alex <>
Date: Mon, 8 Dec 2025 18:11:42 +0000 (+0100)
Subject: day08: part2
X-Git-Url: https://aoc.elinar.fr/?a=commitdiff_plain;h=de7164079e5eeed35608870146ec5dc43280fee7;p=aoc_2025

day08: part2
---

diff --git a/src/day08.rs b/src/day08.rs
index cdd2abb..ba314cf 100644
--- a/src/day08.rs
+++ b/src/day08.rs
@@ -95,11 +95,63 @@ impl Puzzle {
         circuits.sort_by(|a, b| b.cmp(a));
         circuits.iter().take(3).product()
     }
+
+    fn part2(&self) -> i64 {
+        let mut connections: Vec<(i64, (usize, usize))> = Vec::new();
+        for i in 0..self.boxes.len() {
+            for j in (i+1)..self.boxes.len() {
+                connections.push((self.boxes[i].dst(self.boxes[j]), (i, j)));
+            }
+        }
+        connections.sort_by(|a, b| a.0.cmp(&b.0));
+
+        let mut connections: Vec<(usize, usize)> = connections.into_iter()
+            .map(|(_, coord)| coord)
+            .collect();
+        //connections.sort();
+
+        let mut circuits: Vec<HashSet<usize>> = Vec::new();
+        let mut it_connections = connections.iter();
+        while let Some((b1, b2)) = it_connections.next() {
+            if let Some(i) = circuits.iter().position(|s| s.contains(b1)) {
+                if let Some(j) = circuits.iter().position(|s| s.contains(b2)) {
+                    circuits.push( circuits[i].union(&circuits[j]).map(|v| *v).collect() );
+                    circuits.remove(i.max(j));
+                    if i != j {
+                        circuits.remove(i.min(j));
+                    }
+                } else {
+                    circuits[i].insert(*b2);
+                }
+            } else if let Some(i) = circuits.iter().position(|s| s.contains(b2)) {
+                if let Some(j) = circuits.iter().position(|s| s.contains(b1)) {
+                    circuits.push( circuits[i].union(&circuits[j]).map(|v| *v).collect() );
+                    circuits.remove(i.max(j));
+                    if i != j {
+                        circuits.remove(i.min(j));
+                    }
+                } else {
+                    circuits[i].insert(*b1);
+                }
+            } else {
+                let mut s: HashSet<usize> = HashSet::new();
+                s.insert(*b1);
+                s.insert(*b2);
+                circuits.push(s);
+            }
+            circuits.sort_by(|a, b| b.len().cmp(&a.len()));
+            if circuits[0].len() == self.boxes.len() {
+                return self.boxes[*b1].x * self.boxes[*b2].x;
+            }
+        }
+        panic!("No circuits with all junctions");
+    }
 }
 
 pub fn run(input: &str) -> Result<(), Box<dyn Error>> {
     let p = Puzzle::new(input);
     println!("part1: {}", p.part1(1000));
+    println!("part2: {}", p.part2());
     Ok(())
 }
 
@@ -132,6 +184,10 @@ mod tests {
 
     #[test]
     fn test_part1() {
-        assert_eq!(40, Puzzle::new(TEST_INPUT).part1(10));
+        assert_eq!(Puzzle::new(TEST_INPUT).part1(10), 40);
+    }
+    #[test]
+    fn test_part2() {
+        assert_eq!(Puzzle::new(TEST_INPUT).part2(), 25272);
     }
 }