2623-memoize.js

/**
 * 2623. Memoize
 * https://leetcode.com/problems/memoize/
 * Difficulty: Medium
 *
 * 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.
 */

/**
 * @param {Function} fn
 * @return {Function}
 */
function memoize(fn) {
  const cache = new Map();

  return (...args) => {
    const key = String(args);
    if (cache.has(key)) {
      return cache.get(key);
    }
    const value = fn(...args);
    cache.set(key, value);
    return value;
  };
}