def dequeue(self):
if self.is_empty():
raise Empty('Queue empty')
oldhead = self._tail._next
if self._size == 1:
self._tail = None
else:
self._tail._next = oldhead._next
self._size -= 1
return oldhead._data
def delete_last(self):
"""Remove and return the rear element of the deque
Raise Empty exception if the deque is empty
"""
if self.is_empty():
raise Empty('Deque is empty')
back = (self._front + self._size - 1) % len(self._data)
item = self._data[back]
self._data[back] = None
self._size -= 1
if 0 < self._size < len(self._data) // 4:
self._resize(len(self._data) // 2)
return item
def dequeue(self):
"""Remove and return the first element of the queue (i.e., FIFO)
Raise Empty exception if the queue is empty
"""
if self.is_empty():
raise Empty('Queue is empty')
item = self._data[self._front]
self._data[self._front] = None
self._front = (self._front + 1) % len(self._data)
self._size -= 1
if 0 < self._size < len(self._data) // 4:
self._resize(len(self._data) // 2)
return item
def last(self):
if self.is_empty():
raise Empty('Deque is empty')
back = (self._front + self._size - 1) % len(self._data)
return self._data[back]
def delete_first(self):
if self.is_empty():
raise Empty('Deque is empty')
return super().dequeue()
def first(self):
if self.is_empty():
raise Empty('Queue empty')
head = self._tail._next
return head._data
def _transfer(self):
while not self._push_stack.is_empty():
item = self._push_stack.pop()
self._pop_stack.push(item)
if self._pop_stack.is_empty():
raise Empty('Queue is empty')
def first(self):
if self.is_empty():
raise Empty('Queue is empty')
return self._data[self._front]
def pop(self):
if self.is_empty():
raise Empty('Stack is empty')
return self._data.pop()
def top(self):
if self.is_empty():
raise Empty('Stack is empty')
return self._data.head.data