Factorial
Easy · rating 1000 · math
Read an integer n (0 ≤ n ≤ 20). Print n! (n factorial). Note 0! = 1.
Editorial
Factorial computes n! = 1·2·…·n, with 0! = 1. Multiply iteratively. Even 20! exceeds 32 bits, so use a 64-bit (or arbitrary-precision) integer.
result = 1
for i in range(2, n+1):
result *= i
print(result)Complexity
Time: O(n). Space: O(1).