Added cocktail shaker sort

pydatastructs/linear_data_structures/__init__.py

@@ -28,6 +28,7 @@
     heapsort,
     matrix_multiply_parallel,
     counting_sort,
-    bucket_sort
+    bucket_sort,
+    cocktail_sort
 )
 __all__.extend(algorithms.__all__)

pydatastructs/linear_data_structures/algorithms.py

@@ -12,6 +12,7 @@
     'matrix_multiply_parallel',
     'counting_sort',
     'bucket_sort',
+    'cocktail_sort'
 ]
 
 def _merge(array, sl, el, sr, er, end, comp):
@@ -546,3 +547,63 @@ def bucket_sort(array: Array, **kwargs) -> Array:
     if _check_type(array, DynamicArray):
         array._modify(force=True)
     return array
+
+def cocktail_sort(array: Array, **kwargs) -> Array:
+    """
+    Performs cocktail sort on the given array.
+
+    Parameters
+    ==========
+
+    array: Array
+        The array which is to be sorted.
+
+    Returns
+    =======
+
+    output: Array
+        The sorted array.
+
+    Examples
+    ========
+
+    >>> from pydatastructs import OneDimensionalArray as ODA, cocktail_sort
+    >>> arr = ODA(int, [5, 78, 1, 0])
+    >>> out = cocktail_sort(arr)
+    >>> str(out)
+    '[0, 1, 5, 78]'
+    >>> arr = ODA(int, [21, 37, 5])
+    >>> out = cocktail_sort(arr)
+    >>> str(out)
+    '[5, 21, 37]'
+
+    References
+    ==========
+
+    .. [1] https://en.wikipedia.org/wiki/Cocktail_shaker_sort
+
+    Note
+    ====
+
+    Since, cocktail sort is a comparison sorting algorithm,
+    custom comparators aren't allowed.
+    The ouput array doesn't contain any `None` value.
+    """
+    def swap(i, j):
+        array[i], array[j] = array[j], array[i]
+    lower = kwargs.get('start', 0)
+    upper = kwargs.get('end', len(array) - 1)
+    swapping = False
+    while (not swapping and upper - lower >= 1):
+        swapping = True
+        for j in range(lower, upper):
+            if array[j + 1] < array[j]:
+                swap(j + 1, j)
+                swapping = False
+        upper = upper - 1
+        for j in range(upper, lower, -1):
+            if array[j - 1] > array[j]:
+                swap(j - 1, j)
+                swapping = False
+        lower = lower + 1
+    return array

pydatastructs/linear_data_structures/tests/test_algorithms.py

@@ -1,7 +1,7 @@
 from pydatastructs import (
     merge_sort_parallel, DynamicOneDimensionalArray,
     OneDimensionalArray, brick_sort, brick_sort_parallel,
-    heapsort, matrix_multiply_parallel, counting_sort, bucket_sort)
+    heapsort, matrix_multiply_parallel, counting_sort, bucket_sort, cocktail_sort)
 from pydatastructs.utils.raises_util import raises
 import random
 
@@ -70,6 +70,20 @@ def test_counting_sort():
                     480, 548, 686, 688, 696, 779]
     assert counting_sort(arr)._data == expected_arr
 
+def test_cocktail_sort():
+    random.seed(1000)
+
+    n = random.randint(10, 20)
+    arr = DynamicOneDimensionalArray(int, 0)
+    for _ in range(n):
+        arr.append(random.randint(1, 1000))
+    for _ in range(n//3):
+        arr.delete(random.randint(0, n//2))
+
+    expected_arr = [102, 134, 228, 247, 362, 373, 448,
+                    480, 548, 686, 688, 696, 779]
+    assert counting_sort(arr)._data == expected_arr
+
 def test_matrix_multiply_parallel():
     ODA = OneDimensionalArray