#2630 - Memoize II

Hard • View on LeetCode • View on GitHub

Problem Description

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.

fn can be any function and there are no constraints on what type of values it accepts. Inputs are considered identical if they are === to each other.

Solution

/**
 * @param {Function} fn
 * @return {Function}
 */
function memoize(fn) {
  const cache = {};
  const idLookup = new Map();
  function generateId(item) {
    return idLookup.get(item) ?? idLookup.set(item, idLookup.size + 1).get(item);
  }
  return (...args) => {
    const key = args.map(generateId).join('-');
    return !cache.hasOwnProperty(key) ? (cache[key] = fn(...args)) : cache[key];
  };
}