[HackerRank][Python] Recursion 3

Recursive Method for Calculating Factorial

factorial(N) = 1 : N <= 1 , N x factorial (N - 1) : otherwise

 

Function Description

Complete the factorial function in the editor below. Be sure to use recursion.

factorial has the following paramter:

• int n: an integer

Returns

• int: the factorial of n

Note: If you fail to use recursion or fail to name your recursive function factorial or Factorial, you will get a score of 0.

Input Format

A single integer, n (the argument to pass to factorial).

Constraints

• 2 <= n <= 12
• Your submission must contain a recursive function named factorial.

#!/bin/python3

import math
import os
import random
import re
import sys

#
# Complete the 'factorial' function below.
#
# The function is expected to return an INTEGER.
# The function accepts INTEGER n as parameter.
#

def factorial(n):
    # Write your code here
    if n <= 1 :
        return 1
    else :
        return n * factorial(n-1)
        
if __name__ == '__main__':
    fptr = open(os.environ['OUTPUT_PATH'], 'w')

    n = int(input().strip())

    result = factorial(n)

    fptr.write(str(result) + '\n')

    fptr.close()

This implementation uses the recursive formula for calculating the factorial of a number. If the input n is less than or equal to 1, then the function returns 1. Otherwise, it calculates n * factorial(n-1) by calling the factorial function recursively with the argument n-1.