day 11, cleaner

.aocrunner.json

@@ -162,7 +162,7 @@
         "solved": true,
         "result": "213625",
         "attempts": [],
-        "time": 54.460336
+        "time": 4.472301
       },
       "part2": {
         "solved": true,
@@ -170,7 +170,7 @@
         "attempts": [
           "299307972"
         ],
-        "time": 130.250605
+        "time": 126.217947
       }
     },
     {

src/day11/index.ts

@@ -2,50 +2,33 @@ import run from "aocrunner"
 
 const parseInput = (rawInput: string) => rawInput.split(' ').map(Number)
 
-function cacheKey(...args) { // good enough
-  return args.map(String).join('\n');
-}
-function memoize<T extends unknown[],U>(fn: (...args: T) => U): (...args: T) => U {
-  const cache = {}; // Saves the values
+const memoize = <T extends unknown[],U>(fn: (...args: T) => U): (...args: T) => U => {
+  const cache = {} // Saves the values
   return (...args) => {
-    const key = cacheKey(...args);
-    if (!cache[key]) { // Not in the cache? Call fn.
-      cache[key] = fn(...args); // Now it's in the cache.
-    }
-    return cache[key];
+    const key = args.join('\n')
+    return cache[key] ?? (cache[key] = fn(...args))
   }
 }
 
+/** How many stones will a stone marked `n` be after `turn` blinks? */
+const count = memoize((n: number, turn: number): number => {
+  if (turn === 0) return 1
+  if (n === 0) return count(1, turn - 1)
+  const digits = Math.floor(Math.log10(n)) + 1
+  if (digits % 2 === 0) {
+    const exp = 10**(digits/2)
+    return count(Math.floor(n / exp), turn - 1) + count(n % exp, turn - 1)
+  }
+  return count(n * 2024, turn - 1)
+})
+
 const part1 = (rawInput: string) => {
   const input = parseInput(rawInput)
-  const blink = (n: number, turn: number): number[] => {
-    if (turn === 0) return [n]
-    if (n === 0) return blink(1, turn - 1)
-    const digits = Math.floor(Math.log10(n)) + 1
-    if (digits % 2 === 0) {
-      const exp = 10**(digits/2)
-      return [
-        ...blink(Math.floor(n / exp), turn - 1),
-        ...blink(n % exp, turn - 1)
-      ]
-    }
-    return blink(n * 2024, turn - 1)
-  }
-  return input.flatMap(s => blink(s, 25)).length
+  return input.reduce((total, s) => total + count(s, 25), 0)
 }
 
 const part2 = (rawInput: string) => {
   const input = parseInput(rawInput)
-  const count = memoize((n: number, turn: number): number => {
-    if (turn === 0) return 1
-    if (n === 0) return count(1, turn - 1)
-    const digits = Math.floor(Math.log10(n)) + 1
-    if (digits % 2 === 0) {
-      const exp = 10**(digits/2)
-      return count(Math.floor(n / exp), turn - 1) + count(n % exp, turn - 1)
-    }
-    return count(n * 2024, turn - 1)
-  })
   return input.reduce((total, s) => total + count(s, 75), 0)
 }