AoC2025: day 8 part 1

Author: martapanc

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

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+import {part1, part2} from "./day08";
+
+describe('2025 Day 8', () => {
+    test('Part 1', async () => {
+        expect(await part1('testInput1', true)).toEqual(40);
+        expect(await part1('input')).toEqual(123234);
+    });
+
+    test('Part 2', async () => {
+        // expect(await part2('testInput1')).toEqual(31);
+        // expect(await part2('input')).toEqual(29379307);
+    });
+});

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

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+import path from "node:path";
+import {readInputLineByLine} from "@utils/io";
+import {Coord3d} from "@utils/grid3d";
+
+export async function part1(inputFile: string, isTestInput: boolean = false) {
+    return await day8(inputFile, findCircuits, isTestInput);
+}
+
+export async function part2(inputFile: string, isTestInput: boolean = false) {
+    return await day8(inputFile, findCircuits, isTestInput);
+}
+
+async function day8(inputFile: string, calcFn?: (boxes: Coord3d[], isTestInput: boolean) => number, isTestInput: boolean = false) {
+    const inputPath = path.join(__dirname, inputFile);
+    const lines = await readInputLineByLine(inputPath);
+    const boxes = lines.map((line) => {
+        const split = line.split(",").map(Number);
+        return new Coord3d(split[0], split[1], split[2]);
+    });
+    return calcFn?.(boxes, isTestInput);
+}
+
+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
+    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]);
+
+    // Union-Find
+    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;
+    }
+
+    function union(a: number, b: number) {
+        a = find(a); b = find(b);
+        if (a === b) return;
+        if (size[a] < size[b]) [a, b] = [b, a];
+        parent[b] = a;
+        size[a] += size[b];
+    }
+
+    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]);
+    }
+    sizes.sort((a, b) => b - a);
+
+    return sizes[0] * sizes[1] * sizes[2];
+}

2024-2025/src/2025/day08/testInput1

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+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

2024-2025/src/utils/grid3d.ts

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+export class Coord3d {
+    constructor(public x: number, public y: number, public z: number) {}
+
+    equals(other: Coord3d): boolean {
+        return this.x === other.x && this.y === other.y && this.z !== other.z;
+    }
+
+    serialize(): string {
+        return `{${this.x},${this.y},${this.z}}`;
+    }
+
+    static deserialize(input: string): Coord3d {
+        const [x, y, z] = input.replace("{", "").replace("}", "").split(',').map(Number);
+        return new Coord3d(x, y, z);
+    }
+
+    toString(): string {
+        return this.serialize();
+    }
+}
+
+
+export interface Coord3d {
+    x: number;
+    y: number;
+    z: number;
+}