def pop(self):
"""Remove and return the element from teh top of the stack.
Raise Empty exception if the stack is empty."""
if self.is_empty():
raise Empty("Can't pop from an empty stack.")
return self._data.pop()
def min(self): # O(1)
"""Return but don't remove (k, v) tuple with minimum key."""
if self.is_empty():
raise Empty("Priority queue is empty.")
pos = self._data.first()
item = pos.element()
return (item._key, item._value)
def first(self):
"""Return the first element of the deque.
Raise Empty exception if the deque is empty.
"""
if self.is_empty():
raise Empty("Deque is empty.")
return self._data[self._front]
def last(self):
"""Return the element at the back of the queue.
Raise Empty exception if the queue is empty.
"""
if self.is_empty():
raise Empty("Queue is empty.")
return self._tail._element
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("Deque is empty.")
return self._delete_node(self._trailer._prev)
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("Deque is empty.")
return self._delete_node(self._header._next)
def pop(self):
"""Remove and return the element from the top of the stack."""
if self.is_empty():
raise Empty("Stack is empty.")
value = self._top._element
self._top = self._top._next
self._size -= 1
return value
def min(self):
"""Return but don't remove (k, v) tuple with minimum key.
Raise Empty exception if empty.
"""
if self.is_empty():
raise Empty("Priority queue is empty.")
item = self._data[0]
return (item._key, item._value)
def first(self):
"""Return the element at the front of the queue.
Raise Empty exception if the queue is empty.
"""
if self.is_empty():
raise Empty("Queue is empty.")
head = self._tail._next
return head._element
def last(self):
"""Return the last element of the deque.
Raise Empty exception if the deque is empty.
"""
if self.is_empty():
raise Empty("Deque is empty.")
last = (self._front + self._size - 1) % len(self._data)
return self._data[last]
def delete_last(self):
"""Remove and return the last element from the deque."""
if self.is_empty():
raise Empty("Queue is empty.")
last = (self._front + self._size - 1) % len(self._data)
answer = self._data[last]
self._data[last] = None
self._size -= 1
if self._size < len(self._data) // 4:
self._resize(len(self._data) // 2)
return answer
def _find_min(self): # O(n)
"""Return Position of item with minimum key."""
if self.is_empty():
raise Empty("Priority queue is empty.")
small = self._data.first()
walk = self._data.after(small)
while walk is not None:
if walk.element() < small.element():
small = walk
walk = self._data.after(walk)
return small
def remove_min(self):
"""Remove and return (k, v) tuple with minimum key.
Raise Empty exception if empty.
"""
if self.is_empty():
raise Empty("Priority queue is empty.")
self._swap(0, len(self._data) - 1)
item = self._data.pop()
self._downheap(0)
return (item._key, item._value)
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.")
value = self._head._element
self._head = self._head._next
self._size -= 1
if self.is_empty():
self._tail = None
return value
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.")
answer = self._data[self._front]
self._data[self._front] = None
self._front = (self._front + 1) % len(self._data)
self._size -= 1
if self._size < len(self._data) // 4:
self._resize(len(self._data) // 2)
return answer
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.")
oldhead = self._tail._next
if self._size == 1:
self._tail = None
else:
self._tail._next = oldhead._next
self._size -= 1
return oldhead._element
def last(self):
"""Return the element at the end of the deque."""
if self.is_empty():
raise Empty("Deque is empty.")
return self._trailer._prev._element
def first(self):
"""Return the element at the front of the deque."""
if self.is_empty():
raise Empty("Deque is empty.")
return self._header._next._element
def remove_min(self): # O(1)
"""Remove and return (k, v) tuple with minimum key."""
if self.is_empty():
raise Empty("Priority queue is empty.")
item = self._data.delete(self._data.first())
return (item._key, item._value)
def first(self):
"""Return the element at the front of the queue"""
if self.is_empty():
raise Empty("Queue is empty.")
return self._head._element
def peek(self):
"""Return the element at the top of the stack."""
if self.is_empty():
raise Empty("Can't peek at an empty stack.")
return self._data[-1]
def peek(self):
"""Return the element at the top of the stack."""
if self.is_empty():
raise Empty("Stack is empty.")
return self._top._element