day8: part2 solution

src/day8.rs

@@ -126,7 +126,23 @@ fn part1(input: &Circuits) -> u64 {
 
 #[aoc(day8, part2)]
 fn part2(input: &Circuits) -> u64 {
-    0
+    let mut circuits = input.clone();
+    circuits.circuits = Vec::from_iter((0..circuits.junctions.len()).map(|i| vec![i]));
+    for (a, b, _d) in circuits
+        .junctions
+        .iter()
+        .enumerate()
+        .combinations(2)
+        .map(|p| (p[0].0, p[1].0, p[0].1.distance(p[1].1)))
+        .sorted_by(|a, b| a.2.partial_cmp(&b.2).unwrap())
+    {
+        circuits.connect(a, b);
+        if circuits.circuits.len() == 1 {
+            return (circuits.junctions[a].pos.0 * circuits.junctions[b].pos.0) as u64;
+        }
+    }
+
+    panic!()
 }
 
 #[cfg(test)]
@@ -161,6 +177,6 @@ mod tests {
 
     #[test]
     fn part2_example() {
-        assert_eq!(part2(&parse(EXAMPLE)), 0);
+        assert_eq!(part2(&parse(EXAMPLE)), 25272);
     }
 }