Add Optimized Shell Sort

Author: ZicsX

sorts/shrink_shell.py

@@ -0,0 +1,66 @@
+"""
+This function implements the shell sort algorithm.
+
+Shell sort is a sorting algorithm that works by first sorting
+elements that are far apart from each other, and then sorting
+elements that are closer together. This reduces the amount of
+swapping that needs to be done, and makes the algorithm more
+efficient.
+
+The algorithm works by first choosing a 'gap' value. This value
+determines how far apart the elements will be that are sorted
+first. The gap is then decreased, and the elements are sorted
+again. This process is repeated until the gap is 1, at which
+point the elements are sorted using insertion sort.
+
+Shell sort is an efficient algorithm that is easy to implement.
+It is a good choice for sorting large arrays of data.
+
+"""
+
+def shell_sort(collection):
+    """Implementation of shell sort algorithm in Python
+    :param collection:  Some mutable ordered collection with heterogeneous
+    comparable items inside
+    :return:  the same collection ordered by ascending
+    
+    >>> shell_sort([3, 2, 1])
+    [1, 2, 3]
+    >>> shell_sort([])
+    []
+    >>> shell_sort([1])
+    [1]
+    """
+
+    # Choose an initial gap value
+    gap = len(collection)
+
+    # Set the gap value to be decreased by a factor of 1.3
+    # after each iteration
+    shrink = 1.3
+
+    # Continue sorting until the gap is 1
+    while gap > 1:
+
+        # Decrease the gap value
+        gap = int(gap / shrink)
+
+        # Sort the elements using insertion sort
+        for i in range(gap, len(collection)):
+            temp = collection[i]
+            j = i
+            while j >= gap and collection[j - gap] > temp:
+                collection[j] = collection[j - gap]
+                j -= gap
+            collection[j] = temp
+
+    return collection
+
+
+if __name__ == "__main__":
+    import doctest
+    doctest.testmod()
+
+    user_input = input("Enter numbers separated by a comma:\n").strip()
+    collection = [int(item) for item in user_input.split(",")]
+    print(shell_sort(collection))