def delete_last(self):
'''Remove and return the element from the back of the deque.
Raise Empty exception if the deque is empty.
'''
if self.is_empty():
raise empty.Empty('Deque is empty')
return self._delete_node(self._trailer._prev)
def pop(self):
"""Remove and return the element from the top of the stack"""
if self.is_empty():
raise empty.Empty('Stack is empty')
answer = self._head._element
self._head = self._head._next
self._size -= 1
return answer
def first(self):
'''Return (but do not remove) the element at the front of the queue.
Raise Empty exception if the queue is empty.
'''
if self.is_empty():
raise empty.Empty("Queue is empty")
return self._data[self._front]
def delete_first(self):
'''Remove and return the element from the front of the deque.
Raise Empty exception if the deque is empty.
'''
if self.is_empty():
raise empty.Empty('Deque is empty')
return self._delete_node(self._header._next)
def top(self):
'''Return (but do not remove) the element at the top of the stack.
Raise Empty exception if the stack is empty.
'''
if self.is_empty():
raise empty.Empty('Stack is empty')
return self._data[-1]
def pop(self):
'''Return and remove the element at the top of the stack.
Raise Empty exception if the stack is empty.
'''
if self.is_empty():
raise empty.Empty('Stack is empty')
print("Removed {} from the stack!".format(self.top()))
if self.top() == self._min_stack[-1]:
self._min_stack.pop()
return self._data.pop()
def dequeue(self):
'''Remove and return the first element of the queue.
Raise Empty exception if the queue is empty.
'''
if self.is_empty():
raise empty.Empty("Queue is empty")
answer = self._data[self._front]
self._data[self._front] = None # help garbage collection
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) # shrinking the underlying array
return answer
def top(self):
"""Return (but do not remove) the element at the top of the stack"""
if self.is_empty():
raise empty.Empty('Stack is empty')
return self._head._element
def first(self):
'''Return (but not remove) an element at the front of the deque'''
if self.is_empty():
raise empty.Empty('Deque is empty')
return self._header._next._element
def last(self):
'''Return (but not remove) an element at the back of the deque'''
if self.is_empty():
raise empty.Empty('Deque is empty')
return self._trailer._prev._element
def min(self):
if not self._min_stack:
raise empty.Empty('Stack is empty')
return self._min_stack[-1]
