💻 Factorial Calculator

def factorial_iterative(n):
    if n < 0: return None
    result = 1
    for i in range(1, n+1):
        result *= i
    return result

def factorial_recursive(n):
    if n < 0: return None
    if n == 0 or n == 1: return 1
    return n * factorial_recursive(n-1)

import math

print("=== Factorial Calculator ===")
print("n! = 1 x 2 x 3 x ... x n
")

while True:
    print("1. Factorial calculate karo")
    print("2. Step-by-step dekho")
    print("3. Factorial table (1-10)")
    print("4. Permutation nPr")
    print("5. Combination nCr")
    print("6. Baahar jao")
    ch = input("Choice: ")
    if ch == "1":
        n = int(input("N: "))
        if n < 0:
            print("Negative number ka factorial nahi hota!")
        else:
            print(f"{n}! = {factorial_iterative(n)}")
    elif ch == "2":
        n = int(input("N (max 10): "))
        steps = " x ".join(str(i) for i in range(1, n+1))
        print(f"{n}! = {steps} = {factorial_iterative(n)}")
    elif ch == "3":
        print("
Factorial Table:")
        for i in range(11):
            print(f"  {i:2}! = {factorial_iterative(i)}")
    elif ch == "4":
        n = int(input("n: "))
        r = int(input("r: "))
        nPr = math.factorial(n) // math.factorial(n-r)
        print(f"{n}P{r} = {nPr}")
    elif ch == "5":
        n = int(input("n: "))
        r = int(input("r: "))
        nCr = math.factorial(n) // (math.factorial(r) * math.factorial(n-r))
        print(f"{n}C{r} = {nCr}")
    elif ch == "6":
        break