Add ShellSort

sorts/shell_sort.py

@@ -0,0 +1,39 @@
+"""
+https://en.wikipedia.org/wiki/Shellsort
+"""
+
+
+def shell_sort(array):
+    """
+    Shell Sort algorithm
+    :param array: the array to be sorted.
+    :return: sorted array.
+    >>> import random
+    >>> array = random.sample(range(-50, 50), 100)
+    >>> shell_sort(array) == sorted(array)
+    True
+    >>> import string
+    >>> array = random.choices(string.ascii_letters + string.digits, k = 100)
+    >>> shell_sort(array) == sorted(array)
+    True
+    >>> array = [random.uniform(-50.0, 50.0) for i in range(100)]
+    >>> shell_sort(array) == sorted(array)
+    True
+    """
+    gap = len(array) >> 1
+    while gap > 0:
+        for i in range(gap, len(array)):
+            insert_value = array[i]
+            j = i - gap
+            while j >= 0 and insert_value < array[j]:
+                array[j + gap] = array[j]
+                j -= gap
+            array[j + gap] = insert_value
+        gap >>= 1
+    return array
+
+
+if __name__ == "__main__":
+    from doctest import testmod
+
+    testmod()