Create stalin_sort.py (#11989)

* Create stalin_sort.py

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* Update stalin_sort.py

* updating DIRECTORY.md

* Update stalin_sort.py

---------

Co-authored-by: pre-commit-ci[bot] <66853113+pre-commit-ci[bot]@users.noreply.github.com>
Co-authored-by: Maxim Smolskiy <mithridatus@mail.ru>
Co-authored-by: MaximSmolskiy <MaximSmolskiy@users.noreply.github.com>

Author: 3 people

DIRECTORY.md

@@ -1301,6 +1301,7 @@
   * [Shell Sort](sorts/shell_sort.py)
   * [Shrink Shell Sort](sorts/shrink_shell_sort.py)
   * [Slowsort](sorts/slowsort.py)
+  * [Stalin Sort](sorts/stalin_sort.py)
   * [Stooge Sort](sorts/stooge_sort.py)
   * [Strand Sort](sorts/strand_sort.py)
   * [Tim Sort](sorts/tim_sort.py)

sorts/stalin_sort.py

@@ -0,0 +1,47 @@
+"""
+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
+"""
+
+
+def stalin_sort(sequence: list[int]) -> list[int]:
+    """
+    Sorts a list using the Stalin sort algorithm.
+
+    >>> 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]
+    """
+    result = [sequence[0]]
+    for element in sequence[1:]:
+        if element >= result[-1]:
+            result.append(element)
+
+    return result
+
+
+if __name__ == "__main__":
+    import doctest
+
+    doctest.testmod()