Answer
The factorial of a non-negative integer n is the product from 1 through n. • By definition, 0 factorial equals 1. • An iterative solution avoids recursive call depth. • Reject negative inputs because factorial is not defined for them in this integer task.
💡 Simple Example
def factorial(n):
if n < 0:
raise ValueError('n must be non-negative')
result = 1
for value in range(2, n + 1):
result *= value
return result
print(factorial(5))
Output
120
⚡ Quick Revision
Factorial multiplies integers from 1 through n, with 0! equal to 1.