Factorial definition

n! = n * (n-1) * ... * 1 and 0! = 1.

Factorial is the product of all integers from 1 to n, denoted n!. For example, 5! = 120.

0! is defined as 1. It is computed as n! = n * (n-1) * ... * 1. Factorial is used in permutation and combination calculations.

Recursive definition

Factorial's recursive definition: 0! = 1, n! = n * (n-1)!. This naturally solves factorial with recursion.

The base case is 0! = 1. The recursive step is n * (n-1)!. Each call decreases n and eventually reaches 0.

Write factorial(n). If n=0 return 1, else n * factorial(n-1). Print 120 with print(factorial(5)).

Show example solution

def factorial(n):
    # Compute factorial
    if n == 0:
        return 1
    return n * factorial(n - 1)
print(factorial(5))