Create slowsort.py

sorts/slowsort.py

@@ -0,0 +1,63 @@
+"""
+Slowsort is a sorting algorithm. It is of humorous nature and not useful.
+It's based on the principle of multiply and surrender,
+a tongue-in-cheek joke of divide and conquer.
+It was published in 1986 by Andrei Broder and Jorge Stolfi
+in their paper Pessimal Algorithms and Simplexity Analysis
+(a parody of optimal algorithms and complexity analysis).
+
+Source: https://en.wikipedia.org/wiki/Slowsort
+"""
+
+from typing import Optional
+
+
+def slowsort(
+    sequence: list, start: Optional[int] = None, end: Optional[int] = None
+) -> None:
+    """
+    Sorts sequence[start..end] (both inclusive) in-place.
+    start defaults to 0 if not given.
+    end defaults to len(sequence) - 1 if not given.
+    It returns None.
+    >>> seq = [1, 6, 2, 5, 3, 4, 4, 5]; slowsort(seq); seq
+    [1, 2, 3, 4, 4, 5, 5, 6]
+    >>> seq = []; slowsort(seq); seq
+    []
+    >>> seq = [2]; slowsort(seq); seq
+    [2]
+    >>> seq = [1, 2, 3, 4]; slowsort(seq); seq
+    [1, 2, 3, 4]
+    >>> seq = [4, 3, 2, 1]; slowsort(seq); seq
+    [1, 2, 3, 4]
+    >>> seq = [9, 8, 7, 6, 5, 4, 3, 2, 1, 0]; slowsort(seq, 2, 7); seq
+    [9, 8, 2, 3, 4, 5, 6, 7, 1, 0]
+    >>> seq = [9, 8, 7, 6, 5, 4, 3, 2, 1, 0]; slowsort(seq, end = 4); seq
+    [5, 6, 7, 8, 9, 4, 3, 2, 1, 0]
+    >>> seq = [9, 8, 7, 6, 5, 4, 3, 2, 1, 0]; slowsort(seq, start = 5); seq
+    [9, 8, 7, 6, 5, 0, 1, 2, 3, 4]
+    """
+    if start is None:
+        start = 0
+
+    if end is None:
+        end = len(sequence) - 1
+
+    if start >= end:
+        return
+
+    mid = (start + end) // 2
+
+    slowsort(sequence, start, mid)
+    slowsort(sequence, mid + 1, end)
+
+    if sequence[end] < sequence[mid]:
+        sequence[end], sequence[mid] = sequence[mid], sequence[end]
+
+    slowsort(sequence, start, end - 1)
+
+
+if __name__ == "__main__":
+    from doctest import testmod
+
+    testmod()