Create stalin_sort.py

sorts/stalin_sort.py

@@ -0,0 +1,63 @@
+"""
+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
+"""
+
+from typing import List
+
+
+def stalin_sort(sequence: List[int]) -> List[int]:
+    """
+    Sorts a list using the Stalin sort algorithm.
+
+    Parameters:
+        sequence (List[int]): A list of non-negative integers.
+
+    Returns:
+        List[int]: A sorted list according to Stalin Sort.
+
+    Raises:
+        TypeError: If the sequence contains non-integers or negative integers.
+
+    Examples:
+    >>> stalin_sort([6, 11, 12, 4, 1, 5])
+    [6, 11, 12]
+
+    >>> stalin_sort([9, 8, 7, 6, 5, 4, 3, 2, 1])
+    [9]
+
+    >>> stalin_sort([5, 0, 4, 3])
+    [5]
+
+    >>> stalin_sort([8, 2, 1])
+    [8]
+
+    >>> stalin_sort([1, .9, 0.0, 0, -1, -.9])
+    Traceback (most recent call last):
+        ...
+    TypeError: Sequence must be a list of non-negative integers
+
+    >>> stalin_sort("Hello world")
+    Traceback (most recent call last):
+        ...
+    TypeError: Sequence must be a list of non-negative integers
+    """
+    if any(not isinstance(x, int) or x < 0 for x in sequence):
+        raise TypeError("Sequence must be a list of non-negative integers")
+
+    if not sequence:
+        return []
+    result = [sequence[0]]
+
+    for item in sequence[1:]:
+        if item >= result[-1]:
+            result.append(item)
+
+    return result
+
+
+if __name__ == "__main__":
+    assert stalin_sort([5, 4, 3, 2, 1]) == [5]
+    assert stalin_sort([7, 9, 4, 3, 5]) == [7, 9]
+    assert stalin_sort([1, 2, 3, 4, 5]) == [1, 2, 3, 4, 5]