Add iterative factorial function in factorial_iterative.py

Implement iterative factorial function with error handling.

Author: KushDutta23

maths/factorial_iterative.py

@@ -0,0 +1,18 @@
+"""
+Factorial using Iteration
+Time Complexity: O(n)
+Space Complexity: O(1)
+"""
+
+def factorial(n: int) -> int:
+    if n < 0:
+        raise ValueError("Factorial not defined for negative numbers")
+
+    result = 1
+    for i in range(1, n + 1):
+        result *= i
+    return result
+
+
+if __name__ == "__main__":
+    print(factorial(5))