solved day 8

Author: shahata

src/2025/day08.js

@@ -0,0 +1,82 @@
+function straightLineDistance3D(a, b) {
+  return Math.sqrt((a.x - b.x) ** 2 + (a.y - b.y) ** 2 + (a.z - b.z) ** 2);
+}
+
+function top3Circuits(junctions) {
+  let circuitCounts = new Map();
+  for (let junction of junctions) {
+    if (junction.circuit === null) continue;
+    circuitCounts.set(
+      junction.circuit,
+      (circuitCounts.get(junction.circuit) || 0) + 1,
+    );
+  }
+  let counts = Array.from(circuitCounts.values());
+  counts.sort((a, b) => b - a);
+  return counts.slice(0, 3).reduce((a, b) => a * b, 1);
+}
+
+function getAllPairs(junctions) {
+  let pairs = [];
+  for (let i = 0; i < junctions.length; i++) {
+    for (let j = i + 1; j < junctions.length; j++) {
+      let a = junctions[i];
+      let b = junctions[j];
+      let dist = straightLineDistance3D(a, b);
+      pairs.push({ a, b, dist });
+    }
+  }
+  return pairs.sort((p1, p2) => p1.dist - p2.dist);
+}
+
+function connectPair(pair, junctions) {
+  let { a, b } = pair;
+  if (a.circuit === null && b.circuit === null) {
+    a.circuit = b.circuit = Symbol();
+  } else if (a.circuit !== null && b.circuit === null) {
+    b.circuit = a.circuit;
+  } else if (a.circuit === null && b.circuit !== null) {
+    a.circuit = b.circuit;
+  } else if (a.circuit !== b.circuit) {
+    let oldCircuit = b.circuit;
+    let newCircuit = a.circuit;
+    for (let j = 0; j < junctions.length; j++) {
+      if (junctions[j].circuit === oldCircuit) {
+        junctions[j].circuit = newCircuit;
+      }
+    }
+  }
+  return pair;
+}
+
+function allConnected(junctions) {
+  let firstCircuit = junctions[0].circuit;
+  if (firstCircuit === null) return false;
+  for (let junction of junctions) {
+    if (junction.circuit !== firstCircuit) {
+      return false;
+    }
+  }
+  return true;
+}
+
+export function part1(input, times = 1000) {
+  let junctions = input.split("\n").map(line => {
+    let [x, y, z] = line.split(",").map(Number);
+    return { x, y, z, circuit: null };
+  });
+  let pairs = getAllPairs(junctions).slice(0, times);
+  for (let i = 0; i < pairs.length; i++) connectPair(pairs[i], junctions);
+  return top3Circuits(junctions);
+}
+
+export function part2(input) {
+  let junctions = input.split("\n").map(line => {
+    let [x, y, z] = line.split(",").map(Number);
+    return { x, y, z, circuit: null };
+  });
+  let pair;
+  let pairs = getAllPairs(junctions);
+  while (!allConnected(junctions)) pair = connectPair(pairs.shift(), junctions);
+  return pair.a.x * pair.b.x;
+}

src/2025/day08.test.js

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+import { part1, part2 } from "./day08.js";
+import { describe, test, expect } from "vitest";
+import readInput from "../utils/read-input.js";
+
+let input = readInput(import.meta.url);
+
+describe("day08 2025", () => {
+  describe("part1", () => {
+    test("it should work for part 1 examples", () => {
+      expect(
+        part1(
+          [
+            "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",
+          ].join("\n"),
+          10,
+        ),
+      ).toEqual(40);
+    });
+
+    test("it should work for part 1 input", () => {
+      expect(part1(input)).toEqual(140008);
+    });
+  });
+
+  describe("part2", () => {
+    test("it should work for part 2 examples", () => {
+      expect(
+        part2(
+          [
+            "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",
+          ].join("\n"),
+        ),
+      ).toEqual(25272);
+    });
+
+    test("it should work for part 2 input", () => {
+      expect(part2(input)).toEqual(9253260633);
+    });
+  });
+});