Python program to find the factorial of a number using recursion

A factorial is positive integer n, and denoted by n!. Then the product of all positive integers less than or equal to n.

For example:

In this article, we are going to calculate the factorial of a number using recursion.

Examples:

Input: 5
Output: 120

Input: 6
Output: 720

Implementation:

If fact(5) is called, it will call fact(4), fact(3), fact(2) and fact(1). So it means keeps calling itself by reducing value by one till it reaches 1.

Python3

# Python 3 program to find
# factorial of given number
def factorial(n):

    # Checking the number
    # is 1 or 0 then
    # return 1
    # other wise return
    # factorial
    if (n==1 or n==0):

        return 1

    else:

        return (n * factorial(n - 1))

# Driver Code
num = 5;
print("number : ",num)
print("Factorial : ",factorial(num))

Output

number :  5
Factorial :  120

Time complexity: O(n)

Space complexity: O(n)