Increase performance for finding Factorial of large numbers

[rao121]

I am using iterative method and recursion method to implement factorial but when finding the same for large numbers,it takes alot of time.Any way to change that?

[hussainmujtaba]

I get your question , the problem of computing factorial has a highly repetitive structure. You can use dynamic programming to solve your problem. The conditions for implementing dynamic programming are

• Overlapping sub-problems
• optimal substructure

Here is a code which may help you to understand what I am trying to say

def DPfact(N):
    arr={}
    if N in arr:
        return arr[N]
    elif N == 0 or N == 1:
        return 1
        arr[N] = 1
    else:
        factorial = N*DPfact(N - 1)
        arr[N] = factorial
    return factorial
    
num=int(input("Enter the number: "))

print("factorial of ",num," (dynamic): ",end="")
print(DPfact(num))

To get a more clear idea on factorial from basics to such advance level,

[rao121]

Thankyou, It kinda helped

[SioSio]

The math module factorial implemented in C is faster than the recursive call.

import math
num=int(input("Enter the number: "))
print(math.factorial(num))

[dev7060]

Here's the inbuilt factorial algorithm in case anyone's interested https://hg.python.org/cpython/file/7...module.c#l1218