feat: 2024 Day 22

Author: mfulton26

2024/day/22/part/1/solve.test.ts

@@ -0,0 +1,13 @@
+import solve from "./solve.ts";
+
+import { assertEquals } from "@std/assert";
+
+Deno.test("example", () => {
+  const input = `\
+1
+10
+100
+2024`;
+
+  assertEquals(solve(input), 37327623);
+});

2024/day/22/part/1/solve.ts

@@ -0,0 +1,10 @@
+import { generateSecrets } from "../../secrets.ts";
+
+export default function solve(input: string) {
+  const initialSecrets = input.split("\n").map(Number);
+  let sum = 0;
+  for (const initialSecret of initialSecrets) {
+    sum += generateSecrets(initialSecret).at(-1)!;
+  }
+  return sum;
+}

2024/day/22/part/2/solve.test.ts

@@ -0,0 +1,13 @@
+import solve from "./solve.ts";
+
+import { assertEquals } from "@std/assert";
+
+Deno.test("example", () => {
+  const input = `\
+1
+2
+3
+2024`;
+
+  assertEquals(solve(input), 23);
+});

2024/day/22/part/2/solve.ts

@@ -0,0 +1,24 @@
+import { generateSecrets } from "../../secrets.ts";
+
+export default function solve(input: string) {
+  const initialSecrets = input.split("\n").map(Number);
+  const sequenceToTotalPrice = new Map<string, number>();
+  for (const initialSecret of initialSecrets) {
+    const sequenceToPrice = new Map<string, number>();
+    const sequence: number[] = [];
+    let prevPrice = Number(initialSecret % 10);
+    for (const secret of generateSecrets(initialSecret)) {
+      if (sequence.length === 4) sequence.shift();
+      const price = secret % 10;
+      sequence.push(price - prevPrice);
+      prevPrice = price;
+      if (sequence.length < 4) continue;
+      const hash = sequence.join(",");
+      if (sequenceToPrice.has(hash)) continue;
+      sequenceToPrice.set(hash, price);
+      const total = sequenceToTotalPrice.get(hash) ?? 0;
+      sequenceToTotalPrice.set(hash, total + price);
+    }
+  }
+  return Math.max(...sequenceToTotalPrice.values());
+}

2024/day/22/secrets.test.ts

@@ -0,0 +1,17 @@
+import { assertEquals } from "@std/assert";
+import { generateSecrets } from "./secrets.ts";
+
+Deno.test("example", () => {
+  assertEquals(generateSecrets(123, { limit: 10 }), [
+    15887950,
+    16495136,
+    527345,
+    704524,
+    1553684,
+    12683156,
+    11100544,
+    12249484,
+    7753432,
+    5908254,
+  ]);
+});

2024/day/22/secrets.ts

@@ -0,0 +1,19 @@
+function mix(secret: bigint, value: bigint) {
+  return value ^ secret;
+}
+
+function prune(secret: bigint) {
+  return secret % 16777216n;
+}
+
+export function generateSecrets(initialSecret: number, { limit = 2000 } = {}) {
+  const result: number[] = [];
+  let secret = BigInt(initialSecret);
+  for (let n = 1; n <= limit; n++) {
+    secret = prune(mix(secret, secret * 64n));
+    secret = prune(mix(secret, secret / 32n));
+    secret = prune(mix(secret, secret * 2048n));
+    result.push(Number(secret));
+  }
+  return result;
+}