feat: 2025 Day 8

Author: mfulton26

2025/day/8/distances.ts

@@ -0,0 +1,14 @@
+import calculateSingleLineDistance from "@lib/calculateSingleLineDistance.ts";
+
+export function calculateDistances(boxes: number[][]) {
+  const distances = new Map<number, Set<(typeof boxes)[number]>>();
+  for (let i = 0; i < boxes.length; i++) {
+    const a = boxes[i];
+    for (let j = i + 1; j < boxes.length; j++) {
+      const b = boxes[j];
+      const distance = Math.abs(calculateSingleLineDistance(a, b));
+      distances.set(distance, new Set([a, b]));
+    }
+  }
+  return distances;
+}

2025/day/8/part/1/solve.test.ts

@@ -0,0 +1,29 @@
+import solve from "./solve.ts";
+
+import { assertEquals } from "@std/assert";
+
+Deno.test("example", () => {
+  const 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`;
+
+  assertEquals(solve(input, { connect: 10 }), 40);
+});

2025/day/8/part/1/solve.ts

@@ -0,0 +1,20 @@
+import { calculateDistances } from "../../distances.ts";
+
+export default function solve(input: string, { connect = 1000 } = {}) {
+  const boxes = input.split("\n").map((line) => line.split(",").map(Number));
+  const boxToCircuit = new Map(boxes.map((box) => [box, new Set([box])]));
+  const stack = Array.from(calculateDistances(boxes)).sort(([a], [b]) => b - a);
+  for (let n = 0; n < connect; n++) {
+    const [, [boxA, boxB]] = stack.pop()!;
+    const circuitA = boxToCircuit.get(boxA)!;
+    const circuitB = boxToCircuit.get(boxB)!;
+    if (circuitA === circuitB) continue;
+    const circuit = circuitA.union(circuitB);
+    for (const box of circuit) boxToCircuit.set(box, circuit);
+  }
+  const circuits = new Set(boxToCircuit.values());
+  return Array.from(circuits, ({ size }) => size)
+    .sort((a, b) => b - a)
+    .slice(0, 3)
+    .reduce((product, size) => product * size, 1);
+}

2025/day/8/part/2/solve.test.ts

@@ -0,0 +1,29 @@
+import solve from "./solve.ts";
+
+import { assertEquals } from "@std/assert";
+
+Deno.test("example", () => {
+  const 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`;
+
+  assertEquals(solve(input), 25272);
+});

2025/day/8/part/2/solve.ts

@@ -0,0 +1,20 @@
+import { calculateDistances } from "../../distances.ts";
+
+export default function solve(input: string) {
+  const boxes = input.split("\n").map((line) => line.split(",").map(Number));
+  const boxToCircuit = new Map(boxes.map((box) => [box, new Set([box])]));
+  const circuits = new Set(boxToCircuit.values());
+  const stack = Array.from(calculateDistances(boxes)).sort(([a], [b]) => b - a);
+  while (circuits.size > 1) {
+    const [, [boxA, boxB]] = stack.pop()!;
+    const circuitA = boxToCircuit.get(boxA)!;
+    const circuitB = boxToCircuit.get(boxB)!;
+    if (circuitA === circuitB) continue;
+    circuits.delete(circuitA);
+    circuits.delete(circuitB);
+    const circuit = circuitA.union(circuitB);
+    for (const box of circuit) boxToCircuit.set(box, circuit);
+    circuits.add(circuit);
+    if (circuits.size === 1) return boxA[0] * boxB[0];
+  }
+}

lib/calculateSingleLineDistance.ts

@@ -0,0 +1,6 @@
+export default function calculateSingleLineDistance(
+  a: readonly number[],
+  b: readonly number[],
+) {
+  return Math.hypot(...a.keys().map((index) => a[index] - b[index]));
+}