Type stalin sort for any comparable items

sorts/stalin_sort.py

@@ -1,43 +1,61 @@
 """
-Stalin Sort algorithm: Removes elements that are out of order.
-Elements that are not greater than or equal to the previous element are discarded.
-Reference: https://medium.com/@kaweendra/the-ultimate-sorting-algorithm-6513d6968420
+A pure Python implementation of the Stalin sort algorithm.
+
+For doctests run the following command:
+    python3 -m doctest -v stalin_sort.py
+
+For manual testing run:
+    python3 stalin_sort.py
 """
 
+from typing import Any, Protocol
 
-def stalin_sort(sequence: list[int]) -> list[int]:
-    """
-    Sorts a list using the Stalin sort algorithm.
 
+class Comparable(Protocol):
+    def __ge__(self, other: Any, /) -> bool: ...
+
+
+def stalin_sort[T: Comparable](sequence: list[T]) -> list[T]:
+    """Sort a list of mutually comparable items using the Stalin sort algorithm.
+
+    Iterates through the sequence and retains elements that are greater than
+    or equal to the last retained element, discarding any out-of-order items.
+
+    Reference: https://medium.com/@kaweendra/the-ultimate-sorting-algorithm-6513d6968420
+
+    Complexity Analysis:
+        - Time Complexity: O(n) where n is the number of elements in the list.
+        - Space Complexity: O(n) auxiliary space for the output list.
+
+    Examples:
     >>> stalin_sort([4, 3, 5, 2, 1, 7])
     [4, 5, 7]
-
     >>> stalin_sort([1, 2, 3, 4])
     [1, 2, 3, 4]
-
     >>> stalin_sort([4, 5, 5, 2, 3])
     [4, 5, 5]
-
     >>> stalin_sort([6, 11, 12, 4, 1, 5])
     [6, 11, 12]
-
     >>> stalin_sort([5, 0, 4, 3])
     [5]
-
     >>> stalin_sort([5, 4, 3, 2, 1])
     [5]
-
     >>> stalin_sort([1, 2, 3, 4, 5])
     [1, 2, 3, 4, 5]
-
     >>> stalin_sort([1, 2, 8, 7, 6])
     [1, 2, 8]
-
     >>> stalin_sort([])
     []
-
     >>> stalin_sort([7])
     [7]
+    >>> stalin_sort([2.5, -1.0, 0.0, 3.2])
+    [2.5, 3.2]
+    >>> stalin_sort(["d", "a", "e", "c", "f"])
+    ['d', 'e', 'f']
+    >>> stalin_sort([1, "a"])
+    Traceback (most recent call last):
+        ...
+    TypeError: '>=' not supported between instances of 'str' and 'int'
     """
     if not sequence:
         return []

tests/test_sorts.py

@@ -244,3 +244,13 @@ def test_bitonic_sort_comparable_items() -> None:
 
     with pytest.raises(TypeError):
         bitonic_sort([1, "two", 3, "four"], 0, 4, 1)
+
+
+def test_stalin_sort_comparable_items() -> None:
+    from sorts.stalin_sort import stalin_sort
+
+    assert stalin_sort(["d", "a", "e", "c", "f"]) == ["d", "e", "f"]
+    assert stalin_sort([2.5, -1.0, 0.0, 3.2]) == [2.5, 3.2]
+
+    with pytest.raises(TypeError):
+        stalin_sort([1, "a"])