# 2623. Memoize

## Description

Given a function fn, return a memoized version of that function.

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 possible input functions: sum, fiband 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.

Example 1:

Input:
fnName = "sum"
actions = ["call","call","getCallCount","call","getCallCount"]
values = [[2,2],[2,2],[],[1,2],[]]
Output: [4,4,1,3,2]
Explanation:
const sum = (a, b) => a + b;
const memoizedSum = memoize(sum);
memoizedSum(2, 2); // "call" - returns 4. sum() was called as (2, 2) was not seen before.
memoizedSum(2, 2); // "call" - returns 4. However sum() was not called because the same inputs were seen before.
// "getCallCount" - total call count: 1
memoizedSum(1, 2); // "call" - returns 3. sum() was called as (1, 2) was not seen before.
// "getCallCount" - total call count: 2


Example 2:

Input:
fnName = "factorial"
actions = ["call","call","call","getCallCount","call","getCallCount"]
values = [[2],[3],[2],[],[3],[]]
Output: [2,6,2,2,6,2]
Explanation:
const factorial = (n) => (n <= 1) ? 1 : (n * factorial(n - 1));
const memoFactorial = memoize(factorial);
memoFactorial(2); // "call" - returns 2.
memoFactorial(3); // "call" - returns 6.
memoFactorial(2); // "call" - returns 2. However factorial was not called because 2 was seen before.
// "getCallCount" - total call count: 2
memoFactorial(3); // "call" - returns 6. However factorial was not called because 3 was seen before.
// "getCallCount" - total call count: 2


Example 3:

Input:
fnName = "fib"
actions = ["call","getCallCount"]
values = [[5],[]]
Output: [8,1]
Explanation:
fib(5) = 8 // "call"
// "getCallCount" - total call count: 1


Constraints:

• 0 <= a, b <= 105
• 1 <= n <= 10
• 0 <= actions.length <= 105
• actions.length === values.length
• actions[i] is one of "call" and "getCallCount"
• fnName is one of "sum", "factorial" and "fib"

## Solutions

• type Fn = (...params: any) => any;

function memoize(fn: Fn): Fn {
const cache: Record<any, any> = {};

return function (...args) {
if (args in cache) {
return cache[args];
}
const result = fn(...args);
cache[args] = 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
*/