Added deque funcationality to Queue (#321)

Author: Arvind-raj06

pydatastructs/miscellaneous_data_structures/queue.py

@@ -23,6 +23,12 @@ class Queue(object):
     dtype : A valid python type
         Optional, by default NoneType if item
         is None.
+        Required only for 'array' implementation.
+    double_ended : bool
+        Optional, by default, False.
+        Set to True if the queue should support
+        additional, appendleft and pop operations
+        from left and right sides respectively.
 
     Examples
     ========
@@ -47,10 +53,12 @@ def __new__(cls, implementation='array', **kwargs):
         if implementation == 'array':
             return ArrayQueue(
                 kwargs.get('items', None),
-                kwargs.get('dtype', int))
+                kwargs.get('dtype', int),
+                kwargs.get('double_ended', False))
         elif implementation == 'linked_list':
             return LinkedListQueue(
-                kwargs.get('items', None)
+                kwargs.get('items', None),
+                kwargs.get('double_ended', False)
             )
         else:
             raise NotImplementedError(
@@ -60,10 +68,24 @@ def __new__(cls, implementation='array', **kwargs):
     def methods(cls):
         return ['__new__']
 
+    def _double_ended_check(self):
+        if not self._double_ended:
+            raise NotImplementedError(
+                    "This method is only supported for "
+                    "double ended queues.")
+
     def append(self, *args, **kwargs):
         raise NotImplementedError(
             "This is an abstract method.")
 
+    def appendleft(self, *args, **kwargs):
+        raise NotImplementedError(
+            "This is an abstract method.")
+
+    def pop(self, *args, **kwargs):
+        raise NotImplementedError(
+            "This is an abstract method.")
+
     def popleft(self, *args, **kwargs):
         raise NotImplementedError(
             "This is an abstract method.")
@@ -76,52 +98,94 @@ def is_empty(self):
 
 class ArrayQueue(Queue):
 
-    __slots__ = ['front']
+    __slots__ = ['_front', '_rear', '_double_ended']
 
-    def __new__(cls, items=None, dtype=NoneType):
+    def __new__(cls, items=None, dtype=NoneType, double_ended=False):
         if items is None:
             items = DynamicOneDimensionalArray(dtype, 0)
         else:
             dtype = type(items[0])
             items = DynamicOneDimensionalArray(dtype, items)
         obj = object.__new__(cls)
-        obj.items, obj.front = items, -1
+        obj.items, obj._front = items, -1
         if items.size == 0:
-            obj.front = -1
+            obj._front = -1
+            obj._rear = -1
         else:
-            obj.front = 0
+            obj._front = 0
+            obj._rear = items._num - 1
+        obj._double_ended = double_ended
         return obj
 
     @classmethod
     def methods(cls):
-        return ['__new__', 'append', 'popleft', 'rear',
-        'is_empty', '__len__', '__str__']
+        return ['__new__', 'append', 'appendleft', 'popleft',
+                'pop', 'is_empty', '__len__', '__str__', 'front',
+                'rear']
 
     def append(self, x):
         if self.is_empty:
-            self.front = 0
+            self._front = 0
             self.items._dtype = type(x)
         self.items.append(x)
+        self._rear += 1
+
+    def appendleft(self, x):
+        self._double_ended_check()
+        temp = []
+        if self.is_empty:
+            self._front = 0
+            self._rear = -1
+        self.items._dtype = type(x)
+        temp.append(x)
+        for i in range(self._front, self._rear + 1):
+            temp.append(self.items._data[i])
+        self.items = DynamicOneDimensionalArray(type(temp[0]), temp)
+        self._rear += 1
 
     def popleft(self):
         if self.is_empty:
             raise IndexError("Queue is empty.")
-        return_value = dc(self.items[self.front])
-        front_temp = self.front
-        if self.front == self.rear:
-            self.front = -1
+        return_value = dc(self.items[self._front])
+        front_temp = self._front
+        if self._front == self._rear:
+            self._front = -1
+            self._rear = -1
         else:
             if (self.items._num - 1)/self.items._size < \
                 self.items._load_factor:
-                self.front = 0
+                self._front = 0
             else:
-                self.front += 1
+                self._front += 1
         self.items.delete(front_temp)
         return return_value
 
+    def pop(self):
+        self._double_ended_check()
+        if self.is_empty:
+            raise IndexError("Queue is empty.")
+
+        return_value = dc(self.items[self._rear])
+        rear_temp = self._rear
+        if self._front == self._rear:
+            self._front = -1
+            self._rear = -1
+        else:
+            if (self.items._num - 1)/self.items._size < \
+                self.items._load_factor:
+                self._front = 0
+            else:
+                self._rear -= 1
+        self.items.delete(rear_temp)
+        return return_value
+
+    @property
+    def front(self):
+        return self._front
+
     @property
     def rear(self):
-        return self.items._last_pos_filled
+        return self._rear
 
     @property
     def is_empty(self):
@@ -132,16 +196,15 @@ def __len__(self):
 
     def __str__(self):
         _data = []
-        for i in range(self.front, self.rear + 1):
+        for i in range(self._front, self._rear + 1):
             _data.append(self.items._data[i])
         return str(_data)
 
-
 class LinkedListQueue(Queue):
 
-    __slots__ = ['queue']
+    __slots__ = ['queue', '_double_ended']
 
-    def __new__(cls, items=None):
+    def __new__(cls, items=None, double_ended=False):
         obj = object.__new__(cls)
         obj.queue = SinglyLinkedList()
         if items is None:
@@ -151,16 +214,29 @@ def __new__(cls, items=None):
                 obj.append(x)
         else:
             raise TypeError("Expected type: list/tuple")
+        obj._double_ended = double_ended
         return obj
 
     @classmethod
     def methods(cls):
-        return ['__new__', 'append', 'popleft', 'rear',
-        'is_empty', '__len__', '__str__', 'front', 'size']
+        return ['__new__', 'append', 'appendleft', 'pop', 'popleft',
+                'is_empty', '__len__', '__str__', 'front', 'rear']
 
     def append(self, x):
         self.queue.append(x)
 
+    def appendleft(self, x):
+        self._double_ended_check()
+        if self._double_ended:
+            self.queue.appendleft(x)
+
+    def pop(self):
+        self._double_ended_check()
+        if self.is_empty:
+            raise IndexError("Queue is empty.")
+        return_value = self.queue.popright()
+        return return_value
+
     def popleft(self):
         if self.is_empty:
             raise IndexError("Queue is empty.")
@@ -169,7 +245,7 @@ def popleft(self):
 
     @property
     def is_empty(self):
-        return self.size == 0
+        return self.__len__() == 0
 
     @property
     def front(self):
@@ -179,12 +255,8 @@ def front(self):
     def rear(self):
         return self.queue.tail
 
-    @property
-    def size(self):
-        return self.queue.size
-
     def __len__(self):
-        return self.size
+        return self.queue.size
 
     def __str__(self):
         return str(self.queue)

pydatastructs/miscellaneous_data_structures/tests/test_queue.py

@@ -30,6 +30,23 @@ def test_ArrayQueue():
     assert q1.popleft() == 3
     assert len(q1) == 0
 
+    q2 = Queue(implementation='array', items=[0], double_ended=True)
+    q2.append(1)
+    q2.append(2)
+    q2.appendleft(3)
+    assert str(q2) == '[3, 0, 1, 2]'
+    assert len(q2) == 4
+    assert q2.popleft() == 3
+    assert q2.pop() == 2
+    assert len(q2) == 2
+    assert q2.popleft() == 0
+    assert q2.pop() == 1
+    assert len(q2) == 0
+
+    q1 = Queue(implementation='array', items=[0])
+    assert raises(NotImplementedError, lambda: q1.appendleft(2))
+
+
 def test_LinkedListQueue():
     q1 = Queue(implementation='linked_list')
     q1.append(1)
@@ -49,7 +66,6 @@ def test_LinkedListQueue():
 
     q1 = Queue(implementation='linked_list',items=['a',None,type,{}])
     assert len(q1) == 4
-    assert q1.size == 4
 
     front = q1.front
     assert front.key == q1.popleft().key
@@ -60,6 +76,23 @@ def test_LinkedListQueue():
 
     assert rear.key == q1.popleft().key
 
+    q1 = Queue(implementation='linked_list', double_ended=True)
+    q1.appendleft(1)
+    q2 = Queue(implementation='linked_list', items=[0, 1])
+    assert raises(NotImplementedError, lambda: q2.appendleft(1))
+    q1 = Queue(implementation='linked_list', items = [0, 1], double_ended=True)
+    q1.appendleft(2)
+    q1.append(3)
+    assert str(q1) == "['2', '0', '1', '3']"
+    assert len(q1) == 4
+    assert q1.popleft().key == 2
+    assert q1.pop().key == 3
+    assert len(q1) == 2
+    assert q1.pop().key == 1
+    assert q1.popleft().key == 0
+    assert len(q1) == 0
+    assert raises(IndexError, lambda: q1.popleft())
+
 def test_PriorityQueue():
     pq1 = PriorityQueue(implementation='linked_list')
     assert _check_type(pq1, LinkedListPriorityQueue) is True