2024 day 11 final

2024/day-11/day11.ts

@@ -1,35 +1,57 @@
-import { Worker } from "node:worker_threads";
+const cache = new Map<string, number>();
 
-export async function part1(input: string) {
+export function part1(input: string) {
 	const lines = input.split("\n");
 	const line = lines[0];
 	const stones = line.split(" ").map(Number);
-	stones.length = 1;
-	// for (let i = 0; i < 75; i++) {
-	// 	console.log(i);
-	// 	stones = blink(stones);
-	// }
-	let final = 0;
-	await Promise.all(
-		stones.map(async (stone) => {
-			const sum = (await new Promise((res) => {
-				const worker = new Worker("./2024/day-11/workers.ts", {
-					workerData: stone,
-				});
-
-				worker.on("message", (result) => {
-					res(result);
-				});
-			})) as number;
-			final += sum;
-		}),
-	);
-
-	return final;
+	let total = 0;
+	for (const stone of stones) {
+		total += count(stone, 25);
+	}
+	return total;
 }
 
 export function part2(input: string) {
 	const lines = input.split("\n");
-	const final = 0;
-	return final;
+	const line = lines[0];
+	const stones = line.split(" ").map(Number);
+	let total = 0;
+	for (const stone of stones) {
+		total += count(stone, 75);
+	}
+	return total;
+}
+
+function count(stone: number, steps: number): number {
+	const key = `${stone},${steps}`;
+
+	if (cache.has(key)) {
+		return cache.get(key) as number;
+	}
+
+	if (steps === 0) {
+		const res = 1;
+		cache.set(key, res);
+		return res;
+	}
+	if (stone === 0) {
+		const res = count(1, steps - 1);
+		cache.set(key, res);
+		return res;
+	}
+	const numberAsString = stone.toString();
+	const numberOfDigits = numberAsString.length;
+	if (numberOfDigits % 2 === 0) {
+		const middle = numberOfDigits / 2;
+		const left = numberAsString.slice(0, middle);
+		const right = numberAsString.slice(middle);
+		const res =
+			count(Number.parseInt(left, 10), steps - 1) +
+			count(Number.parseInt(right, 10), steps - 1);
+		cache.set(key, res);
+		return res;
+	}
+	const res = count(stone * 2024, steps - 1);
+	cache.set(key, res);
+	return res;
 }