Add automorphic number check algorithm

Author: ShreyasKudahalli

maths/automorphic_number.py

@@ -1,8 +1,15 @@
 def is_automorphic(n: int) -> bool:
     """
     Check if a number is an Automorphic Number.
+
     A number is automorphic if its square ends with the number itself.
 
+    Args:
+        n: A non-negative integer.
+
+    Returns:
+        True if n is automorphic, False otherwise.
+
     Examples:
     >>> is_automorphic(5)
     True
@@ -12,9 +19,17 @@ def is_automorphic(n: int) -> bool:
     True
     >>> is_automorphic(7)
     False
+    >>> is_automorphic(-5)
+    Traceback (most recent call last):
+        ...
+    ValueError: n must be a non-negative integer
 
-    Time Complexity: O(d) where d is number of digits
+    Time Complexity:
+        O(d) where d is the number of digits of n.
     """
+    if n < 0:
+        raise ValueError("n must be a non-negative integer")
+
     square = n * n
     return str(square).endswith(str(n))