solved day 22

Author: shahata

src/2024/day22.js

@@ -0,0 +1,37 @@
+function hash(n) {
+  n = (n ^ (n * 64n)) % 16777216n;
+  n = (n ^ (n / 32n)) % 16777216n;
+  n = (n ^ (n * 2048n)) % 16777216n;
+  return n;
+}
+
+export function part1(input) {
+  let numbers = input.split("\n").map(BigInt);
+  for (let i = 0; i < 2000; i++) numbers = numbers.map(hash);
+  return numbers.reduce((a, b) => a + b, 0n);
+}
+
+export function part2(input) {
+  let numbers = input.split("\n").map(BigInt);
+  let diffs = numbers.map(() => []);
+  let cache = new Map();
+  let max = 0;
+  for (let i = 0; i < 2000; i++) {
+    numbers = numbers.map((prev, j) => {
+      let next = hash(prev);
+      diffs[j].push(Number((next % 10n) - (prev % 10n)));
+      if (diffs[j].length >= 4) {
+        let key = diffs[j].slice(-4).join(",");
+        let value = cache.get(key) || { sum: 0, set: new Set() };
+        if (!value.set.has(j)) {
+          value.set.add(j);
+          value.sum += Number(next % 10n);
+          max = Math.max(max, value.sum);
+        }
+        cache.set(key, value);
+      }
+      return next;
+    });
+  }
+  return max;
+}

src/2024/day22.spec.js

@@ -0,0 +1,26 @@
+import { part1, part2 } from "./day22.js";
+import readInput from "../utils/read-input.js";
+
+const input = readInput(import.meta.url);
+
+describe("day22 2024", () => {
+  describe("part1", () => {
+    test("it should work for part 1 examples", () => {
+      expect(part1(["1", "10", "100", "2024"].join("\n"))).toEqual(37327623n);
+    });
+
+    test("it should work for part 1 input", () => {
+      expect(part1(input)).toEqual(17612566393n);
+    });
+  });
+
+  describe("part2", () => {
+    test("it should work for part 2 examples", () => {
+      expect(part2(["1", "2", "3", "2024"].join("\n"))).toEqual(23);
+    });
+
+    test("it should work for part 2 input", () => {
+      expect(part2(input)).toEqual(1968);
+    });
+  });
+});