Finish part-2

2025/day-08/src/part2.rs

@@ -1,11 +1,112 @@
-use miette::Result;
+use glam::Vec3;
+use miette::miette;
+use std::str::FromStr;
+
+fn vec3_from_str(s: &str) -> Result<Vec3, String> {
+    let coords = s
+        .trim()
+        .split(',')
+        .map(|x| {
+            x.parse::<f32>()
+                .map_err(|_| "Invalid coordinate value".to_string())
+        })
+        .collect::<Result<Vec<_>, _>>()?;
+    if coords.len() == 3 {
+        let vec = Vec3::new(coords[0], coords[1], coords[2]);
+        return Ok(vec);
+    }
+
+    Err("Expected exactly 3 coordinates".to_string())
+}
+
+#[derive(Debug, Clone)]
+struct UnionFind {
+    parent: Vec<usize>,
+    size: Vec<usize>,
+}
+
+impl UnionFind {
+    fn new(n: usize) -> Self {
+        Self {
+            parent: (0..n).collect(),
+            size: vec![1; n],
+        }
+    }
+
+    fn find(&mut self, x: usize) -> usize {
+        if self.parent[x] != x {
+            self.parent[x] = self.find(self.parent[x]);
+        }
+        self.parent[x]
+    }
+
+    fn union(&mut self, mut x: usize, mut y: usize) {
+        x = self.find(x);
+        y = self.find(y);
+        if x == y {
+            return;
+        }
+        if self.size[x] < self.size[y] {
+            (x, y) = (y, x);
+        }
+        self.parent[y] = x;
+        self.size[x] += self.size[y];
+    }
+}
+
+#[derive(Debug, Clone)]
+struct Coordinates(Vec<Vec3>);
+
+impl Coordinates {
+    fn solve(&self) -> usize {
+        let n = self.0.len();
+
+        let mut pairs = Vec::new();
+        for i in 0..n {
+            for j in (i + 1)..n {
+                let dist = self.0[i].distance(self.0[j]);
+                pairs.push((dist, i, j));
+            }
+        }
+
+        pairs.sort_by(|a, b| a.0.partial_cmp(&b.0).unwrap());
+
+        let mut uf = UnionFind::new(n);
+        let mut last_pair = (0, 0);
+        let mut num_circuits = n;
+
+        for (_, i, j) in &pairs {
+            if uf.find(*i) != uf.find(*j) {
+                uf.union(*i, *j);
+                last_pair = (*i, *j);
+                num_circuits -= 1;
+
+                if num_circuits == 1 {
+                    break;
+                }
+            }
+        }
+        (self.0[last_pair.0].x as usize) * (self.0[last_pair.1].x as usize)
+    }
+}
+
+impl FromStr for Coordinates {
+    type Err = String;
+    fn from_str(s: &str) -> Result<Self, Self::Err> {
+        let coords = s
+            .lines()
+            .map(vec3_from_str)
+            .collect::<Result<Vec<_>, _>>()?;
+        Ok(Self(coords))
+    }
+}
 
 #[tracing::instrument]
 #[allow(clippy::missing_panics_doc)]
 #[allow(clippy::missing_errors_doc)]
-pub fn process(input: &str) -> Result<usize> {
-    todo!("day xx - part 2");
-    Ok(0)
+pub fn process(input: &str) -> miette::Result<usize> {
+    let coords = Coordinates::from_str(input).map_err(|e| miette!("{e}"))?;
+    Ok(coords.solve())
 }
 
 #[cfg(test)]
@@ -13,10 +114,28 @@ mod tests {
     use super::*;
 
     #[test]
-    fn test_process() -> Result<()> {
-        let input = "";
-        todo!("haven't built test yet");
-        let result = 0;
+    fn test_process() -> miette::Result<()> {
+        let input = "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";
+        let result = 25272;
         assert_eq!(process(input)?, result);
         Ok(())
     }