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.
Example 1:
Input
"sum"
["call","call","getCallCount","call","getCallCount"][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); // Returns 4. sum() was called as (2, 2) was not seen before.
memoizedSum(2, 2); // Returns 4. However sum() was not called because the same inputs were seen before.
// Total call count: 1
memoizedSum(1, 2); // Returns 3. sum() was called as (1, 2) was not seen before.
// Total call count: 2
Example 2:
Input
"factorial"
["call","call","call","getCallCount","call","getCallCount"][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); // Returns 2.
memoFactorial(3); // Returns 6.
memoFactorial(2); // Returns 2. However factorial was not called because 2 was seen before.
// Total call count: 2
memoFactorial(3); // Returns 6. However factorial was not called because 3 was seen before.
// Total call count: 2
Example 3:
Input
"fib"
["call","getCallCount"][5],[]]
Output
[8,1]
Explanation
fib(5) = 8
// Total call count: 1
Constraints:
- 0 <= a, b <= 105
- 1 <= n <= 10
- at most 105 function calls
- at most 105 attempts to access callCount
- input function is sum, fib, or factorial
/**
* @param {Function} fn
*/
function memoize(fn) {
//sum, fib, factorial을 파악
//input된 sum , fib , fcatorial이 memoize(fn) => fn= sum, fib, fac
//배열에 다시 넣는다.
const memo = {}
return function(...args) {
//...args =>[[1,2]] 풀어서 1,2 / 2,2 / 없음 /1,2 / 없음
//call은 함수 호출해서 계산 , getCallCount 호출한 call이 몇갠지 중복x
//fn(...args) =>[4,4,2,3,3] =>call은 문제없음, getCallCount문제
// 함수실행시 call count되게끔
// 한개씩 더하게끔 되어있다. 4 4 call할때마다 callcount가 1개씩 올라간다.
//[] 아무것도 없을경우 => getcallcount 하도록함.
//중복된값은 memo 해놓고 넘어가고, 새로운값만 계산하도록
// 배열, 객체를 만들고 값을 확인해가는것
// console.log(memo[args])
if (memo[args]===undefined){
//args는 undefined,1,2로 구성되어있다. {}를 이용하여 key,value 짝을지어 중복된값을 방지한다.
//undefined => call값
memo[args]=fn(...args)
}
//return을 한다면 배열에 자동으로 값이 삽입
return memo[args]
// return fn(...args)
}
}
/**
* 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
*/
