Memoize

64.8% acceptance

Mar 2, 2026

760

119

Given a function fn, return a memoized version of that function. A memoized function is a function that will never be called twice with the same inputs. Instead it will return a cached value. You can assume there are 3 possible input functions: sum, fib, and factorial. sum accepts two integers a and b and returns a + b. Assume that if a value has already been cached for the arguments (b, a) where a != b, it cannot be used for the arguments (a, b). For example, if the arguments are (3, 2) and (2, 3), two separate calls should be made. fib accepts a single integer n and returns 1 if n <= 1 or fib(n - 1) + fib(n - 2) otherwise. factorial accepts a single integer n and returns 1 if n <= 1 or factorial(n - 1) * n otherwise.

Solution

TypeScript

Time O(1)

Space O(n)

LeetCode

solution.ts

type Fn = (...params: number[]) => number;

function memoize(fn: Fn): Fn {
  const cache = new Map<string, number>();
  return function (...args: number[]): number {
  const key = JSON.stringify(args);
  if (cache.has(key)) return cache.get(key)!;
  const result = fn(...args);
  cache.set(key, result);
  return result;
  };
}

/**
 * let callCount = 0;
 * const memoizedFn = memoize(function (a, b) {
 *   callCount += 1;
 *   return a + b;
 * })
 * memoizedFn(2, 3) // 5
 * memoizedFn(2, 3) // 5
 * console.log(callCount) // 1
 */