Extra Long Factorials | Medium

The factorial of the integer n, written n!, is defined as:

n! = n X (n - 1) X (n - 2) X … X 3 X 2 X 1

Calculate and print the factorial of a given integer.

For example, if n = 30, we calculate 30 X 29 X 28 X … X 2 X 1 and get 265252859812191058636308480000000.

Function Description

Complete the extraLongFactorials function in the editor below. It should print the result and return.

extraLongFactorials has the following parameter(s):

• n: an integer

Note: Factorials of n > 20 can’t be stored even in a 64 - bit long long variable. Big integers must be used for such calculations. Languages like Java, Python, Ruby etc. can handle big integers, but we need to write additional code in C/C++ to handle huge values.

We recommend solving this challenge using BigIntegers.

Input Format

Input consists of a single integer n

Output Format

Print the factorial of n.

Sample Input

25

Sample Output

15511210043330985984000000

My Solution

function extraLongFactorials(n) {
  return [...Array(n)].reduce((a, _, i) => a * BigInt(i + 1), 1n).toString()
}

const r1 = extraLongFactorials(25)
console.log(`실행 결과: ${r1}, 기대값: 15511210043330985984000000`)
const r2 = extraLongFactorials(45)
console.log(`실행 결과: ${r2}, 기대값: 119622220865480194561963161495657715064383733760000000000`)