Add Kaprekar constant routine algorithm

scripts/maths/kaprekar_constant.py

@@ -0,0 +1,54 @@
+def kaprekar_routine(number: int) -> int:
+    """
+    Find steps to Kaprekar constant (6174) bro.
+    Link: https://wikipedia.org
+
+    >>> kaprekar_routine(3524)
+    3
+    >>> kaprekar_routine(6174)
+    0
+    """
+
+    # Checking if the number is 4 digits, throwing an error if not bro
+    if not (1000 <= number <= 9999):
+        raise ValueError("The number must be 4 digits bro!")
+
+    # If someone enters all same digits like 1111, loop breaks. Blocking it here
+    if len(set(str(number))) < 2:
+        raise ValueError(
+            "Digits cannot be all the same bro, make at least two different!"
+        )
+
+    kaprekar_target = 6174
+    steps = 0
+
+    # We are here until the number becomes 6174 bro, loop keeps spinning
+    while number != kaprekar_target:
+        # Padding the number to 4 digits and making it a string bro
+        digits = f"{number:04d}"
+
+        # Sorting digits from biggest to smallest and joining them
+        descending = int("".join(sorted(digits, reverse=True)))
+
+        # Sorting digits from smallest to biggest and joining them
+        ascending = int("".join(sorted(digits)))
+
+        # Subtracting smallest from biggest, finding new number and increasing steps bro
+        number = descending - ascending
+        steps += 1
+
+        # Infinite loop protection just in case we break something, spins 7 times max
+        if steps > 7:
+            break
+
+    return steps
+
+
+if __name__ == "__main__":
+    import doctest
+
+    # Running the test engine that the bots are checking
+    doctest.testmod()
+
+    # Just a small example here to test it for myself
+    print(f"Our number locked in exactly {kaprekar_routine(3524)} steps bro!")