AoC2025: day 8 part 2 refactor

Author: martapanc

2024-2025/src/2025/day08/day08.ts

@@ -24,20 +24,17 @@ function dist(a: Coord3d, b: Coord3d): number {
     return Math.sqrt((a.x - b.x) ** 2 + (a.y - b.y) ** 2 + (a.z - b.z) ** 2);
 }
 
-function findCircuits(boxes: Coord3d[], isTestInput: boolean): number {
-    const n = boxes.length;
-    const k = isTestInput ? Math.floor(n / 2) : n;
-
-    // Collect all pairs sorted by distance
+function sortedPairs(boxes: Coord3d[]): [number, number, number][] {
     const pairs: [number, number, number][] = [];
-    for (let i = 0; i < n; i++) {
-        for (let j = i + 1; j < n; j++) {
+    for (let i = 0; i < boxes.length; i++) {
+        for (let j = i + 1; j < boxes.length; j++) {
             pairs.push([dist(boxes[i], boxes[j]), i, j]);
         }
     }
-    pairs.sort((a, b) => a[0] - b[0]);
+    return pairs.sort((a, b) => a[0] - b[0]);
+}
 
-    // Union-Find
+function makeUnionFind(n: number) {
     const parent = Array.from({length: n}, (_, i) => i);
     const size = new Array(n).fill(1);
 
@@ -49,19 +46,28 @@ function findCircuits(boxes: Coord3d[], isTestInput: boolean): number {
         return x;
     }
 
-    function union(a: number, b: number) {
+    function union(a: number, b: number): boolean {
         a = find(a); b = find(b);
-        if (a === b) return;
+        if (a === b) return false;
         if (size[a] < size[b]) [a, b] = [b, a];
         parent[b] = a;
         size[a] += size[b];
+        return true;
     }
 
+    return { find, union, size };
+}
+
+function findCircuits(boxes: Coord3d[], isTestInput: boolean): number {
+    const n = boxes.length;
+    const k = isTestInput ? Math.floor(n / 2) : n;
+    const pairs = sortedPairs(boxes);
+    const { find, union, size } = makeUnionFind(n);
+
     for (let i = 0; i < k; i++) {
         union(pairs[i][1], pairs[i][2]);
     }
 
-    // Collect circuit sizes via root nodes
     const sizes: number[] = [];
     for (let i = 0; i < n; i++) {
         if (find(i) === i) sizes.push(size[i]);
@@ -73,36 +79,14 @@ function findCircuits(boxes: Coord3d[], isTestInput: boolean): number {
 
 function findCircuitsPart2(boxes: Coord3d[], _isTestInput: boolean): number {
     const n = boxes.length;
-
-    const pairs: [number, number, number][] = [];
-    for (let i = 0; i < n; i++) {
-        for (let j = i + 1; j < n; j++) {
-            pairs.push([dist(boxes[i], boxes[j]), i, j]);
-        }
-    }
-    pairs.sort((a, b) => a[0] - b[0]);
-
-    const parent = Array.from({length: n}, (_, i) => i);
-    const size = new Array(n).fill(1);
-
-    function find(x: number): number {
-        while (parent[x] !== x) {
-            parent[x] = parent[parent[x]];
-            x = parent[x];
-        }
-        return x;
-    }
+    const pairs = sortedPairs(boxes);
+    const { union } = makeUnionFind(n);
 
     let components = n;
     for (const [, i, j] of pairs) {
-        const ri = find(i), rj = find(j);
-        if (ri === rj) continue;
-        const [big, small] = size[ri] >= size[rj] ? [ri, rj] : [rj, ri];
-        parent[small] = big;
-        size[big] += size[small];
-        components--;
-        if (components === 1) {
-            return boxes[i].x * boxes[j].x;
+        if (union(i, j)) {
+            components--;
+            if (components === 1) return boxes[i].x * boxes[j].x;
         }
     }