2623-memoize.ts

// Title: Memoize
// 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.
//     You can assume there are 3 possible input functions: sum, fib, and factorial.
//         sum accepts two integers a and b and returns a + b.
//         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.
// Link: https://leetcode.com/problems/memoize/

type Fn = (...params: any) => any;

function memoize(fn: Fn): Fn {
  const cache = new Map<string, any>();

  return function (...args) {
    const cacheKey = JSON.stringify(args);

    if (!cache.has(cacheKey)) cache.set(cacheKey, fn(...args));

    return cache.get(cacheKey);
  };
}

/** 
 * 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 
 */