Restructured queue.py and stack.py (#152)

Author: HarsheetKakar

pydatastructs/miscellaneous_data_structures/queue.py

@@ -1,5 +1,5 @@
 from pydatastructs.linear_data_structures import DynamicOneDimensionalArray, SinglyLinkedList
-from pydatastructs.utils.misc_util import NoneType, LinkedListNode
+from pydatastructs.utils.misc_util import NoneType, LinkedListNode, _check_type
 from copy import deepcopy as dc
 
 __all__ = [
@@ -46,10 +46,9 @@ def __new__(cls, implementation='array', **kwargs):
             return ArrayQueue(
                 kwargs.get('items', None),
                 kwargs.get('dtype', int))
-        elif implementation == 'linkedlist':
+        elif implementation == 'linked_list':
             return LinkedListQueue(
-                kwargs.get('items', None),
-                kwargs.get('dtype', NoneType)
+                kwargs.get('items', None)
             )
         raise NotImplementedError(
                 "%s hasn't been implemented yet."%(implementation))
@@ -94,7 +93,7 @@ def append(self, x):
 
     def popleft(self):
         if self.is_empty:
-            raise ValueError("Queue is empty.")
+            raise IndexError("Queue is empty.")
         return_value = dc(self.items[self.front])
         front_temp = self.front
         if self.front == self.rear:
@@ -128,53 +127,45 @@ def __str__(self):
 
 class LinkedListQueue(Queue):
 
-    __slots__ = ['front', 'rear', 'size', '_dtype']
+    __slots__ = ['queue']
 
-    def __new__(cls, items=None, dtype=NoneType):
+    def __new__(cls, items=None):
         obj = object.__new__(cls)
         obj.queue = SinglyLinkedList()
-        obj._dtype = dtype
         if items is None:
             pass
         elif type(items) in (list, tuple):
-            if len(items) != 0 and dtype is NoneType:
-                obj._dtype = type(items[0])
             for x in items:
-                if type(x) == obj._dtype:
-                    obj.queue.append(x)
-                else:
-                    raise TypeError("Expected %s but got %s"%(obj._dtype, type(x)))
+                obj.append(x)
         else:
             raise TypeError("Expected type: list/tuple")
-        obj.front = obj.queue.head
-        obj.rear = obj.queue.tail
-        obj.size = obj.queue.size
         return obj
 
     def append(self, x):
-        if self._dtype is NoneType:
-            self._dtype = type(x)
-        elif type(x) is not self._dtype:
-            raise TypeError("Expected %s but got %s"%(self._dtype, type(x)))
-        self.size += 1
         self.queue.append(x)
-        if self.front is None:
-            self.front = self.queue.head
-        self.rear = self.queue.tail
 
     def popleft(self):
         if self.is_empty:
-            raise ValueError("Queue is empty.")
-        self.size -= 1
+            raise IndexError("Queue is empty.")
         return_value = self.queue.pop_left()
-        self.front = self.queue.head
-        self.rear = self.queue.tail
         return return_value
 
     @property
     def is_empty(self):
         return self.size == 0
 
+    @property
+    def front(self):
+        return self.queue.head
+
+    @property
+    def rear(self):
+        return self.queue.tail
+
+    @property
+    def size(self):
+        return self.queue.size
+
     def __len__(self):
         return self.size
 

pydatastructs/miscellaneous_data_structures/stack.py

@@ -1,4 +1,4 @@
-from pydatastructs.linear_data_structures import DynamicOneDimensionalArray
+from pydatastructs.linear_data_structures import DynamicOneDimensionalArray, SinglyLinkedList
 from pydatastructs.utils.misc_util import _check_type, NoneType
 from copy import deepcopy as dc
 
@@ -51,6 +51,10 @@ def __new__(cls, implementation='array', **kwargs):
             return ArrayStack(
                 kwargs.get('items', None),
                 kwargs.get('dtype', int))
+        if implementation == 'linked_list':
+            return LinkedListStack(
+                kwargs.get('items',None)
+            )
         raise NotImplementedError(
                 "%s hasn't been implemented yet."%(implementation))
 
@@ -64,11 +68,13 @@ def pop(self, *args, **kwargs):
 
     @property
     def is_empty(self):
-        return None
+        raise NotImplementedError(
+              "This is an abstract method.")
 
     @property
     def peek(self):
-        return None
+        raise NotImplementedError(
+              "This is an abstract method.")
 
 class ArrayStack(Stack):
 
@@ -90,7 +96,7 @@ def push(self, x):
 
     def pop(self):
         if self.is_empty:
-            raise ValueError("Stack is empty")
+            raise IndexError("Stack is empty")
 
         top_element = dc(self.items[self.items._last_pos_filled])
         self.items.delete(self.items._last_pos_filled)
@@ -104,8 +110,58 @@ def is_empty(self):
     def peek(self):
         return self.items[self.items._last_pos_filled]
 
+    def __len__(self):
+        return self.items._num
+
     def __str__(self):
         """
         Used for printing.
         """
         return str(self.items._data)
+
+
+class LinkedListStack(Stack):
+
+    __slots__ = ['stack']
+
+    def __new__(cls, items=None):
+        obj = object.__new__(cls)
+        obj.stack = SinglyLinkedList()
+        if items is None:
+            pass
+        elif type(items) in (list, tuple):
+            for x in items:
+                obj.push(x)
+        else:
+            raise TypeError("Expected type: list/tuple")
+        return obj
+
+    def push(self, x):
+        self.stack.append_left(x)
+
+    def pop(self):
+        if self.is_empty:
+            raise IndexError("Stack is empty")
+        return self.stack.pop_left()
+
+    @property
+    def is_empty(self):
+        return self.__len__() == 0
+
+    @property
+    def peek(self):
+        return self.top.data
+
+    @property
+    def top(self):
+        return self.stack.head
+
+    @property
+    def size(self):
+        return self.stack.size
+
+    def __len__(self):
+        return self.stack.size
+
+    def __str__(self):
+        return str(self.stack)

pydatastructs/miscellaneous_data_structures/tests/test_queue.py

@@ -17,14 +17,12 @@ def test_Queue():
     assert len(q1) == 0
 
     q1 = Queue()
-    raises(ValueError, lambda: q1.popleft())
+    raises(IndexError, lambda: q1.popleft())
 
-    q1 = Queue(implementation='linkedlist')
+    q1 = Queue(implementation='linked_list')
     q1.append(1)
-    assert raises(TypeError, lambda: q1.append('a'))
-    assert raises(TypeError, lambda: Queue(implementation='linkedlist', items=[0], dtype=str))
-    assert raises(TypeError, lambda: Queue(implementation='linkedlist', items={0, 1}))
-    q1 = Queue(implementation='linkedlist', items = [0, 1])
+    assert raises(TypeError, lambda: Queue(implementation='linked_list', items={0, 1}))
+    q1 = Queue(implementation='linked_list', items = [0, 1])
     q1.append(2)
     q1.append(3)
     assert str(q1) == '[0, 1, 2, 3]'
@@ -35,4 +33,17 @@ def test_Queue():
     assert q1.popleft().data == 2
     assert q1.popleft().data == 3
     assert len(q1) == 0
-    raises(ValueError, lambda: q1.popleft())
+    raises(IndexError, lambda: q1.popleft())
+
+    q1 = Queue(implementation='linked_list',items=['a',None,type,{}])
+    assert len(q1) == 4
+    assert q1.size == 4
+
+    front = q1.front
+    assert front.data == q1.popleft().data
+
+    rear = q1.rear
+    for _ in range(len(q1)-1):
+        q1.popleft()
+
+    assert rear.data == q1.popleft().data

pydatastructs/miscellaneous_data_structures/tests/test_stack.py

@@ -14,7 +14,34 @@ def test_Stack():
     assert s.pop() == 2
     assert s.pop() == 1
     assert s.is_empty is True
-    assert raises(ValueError, lambda : s.pop())
+    assert raises(IndexError, lambda : s.pop())
     _s = Stack(items=[1, 2, 3])
     assert str(_s) == '[1, 2, 3]'
+    assert len(_s) == 3
     assert raises(NotImplementedError, lambda: Stack(implementation=''))
+
+    s = Stack(implementation='linked_list')
+    s.push(1)
+    s.push(2)
+    s.push(3)
+    assert s.peek == 3
+    assert str(s) == '[3, 2, 1]'
+    assert s.pop().data == 3
+    assert s.pop().data == 2
+    assert s.pop().data == 1
+    assert s.is_empty is True
+    assert raises(IndexError, lambda : s.pop())
+    _s = Stack(implementation='linked_list',items=[1, 2, 3])
+    assert str(_s) == '[3, 2, 1]'
+    assert len(_s) == 3
+
+    s = Stack(implementation='linked_list',items=['a',None,type,{}])
+    assert len(s) == 4
+    assert s.size == 4
+
+    top = s.top
+    assert top.data == s.pop().data
+
+    peek = s.peek
+    assert peek == s.pop().data
+    assert raises(TypeError, lambda: Stack(implementation='linked_list', items={0, 1}))