def first(self):
"""
Return (but do not remove) the element at the front of the deque.
"""
if self.is_empty():
raise Empty('Deque is empty')
# real item just after header
return self._header._next._element
def remove_min(self):
"""
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 last(self):
"""
Return (but do not remove) the element at the back of the deque.
"""
if self.is_empty():
raise Empty('Deque is empty')
# real item just before trailer
return self._trailer._prev._element
def first(self):
"""
Return (but do not remove) the element at the front of the queue.
"""
if self.is_empty():
raise Empty('Queue is empty')
# front aligned with head of list
return self._head._element
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('Queue is empty')
return self._data[self._front]
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('Stack is empty')
# top of stack is at head of list
return self._head._element
def pop(self):
"""
Remove and return the element from the top of the stack (i.e., LIFO).
Raise Empty exception if the stack is empty.
"""
if self.is_empty():
raise Empty('Stack is empty')
# remove last item from list
return self._data.pop()
def min(self):
"""
Return but do not 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 min(self):
"""
Return but do not remove (k, v) tuple with minimum key.
"""
if self.is_empty():
raise Empty('Priority queue is empty.')
p = self._data.first()
item = p.element()
return item._key, item._value
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('Queue is empty')
head = self._tail._next
return head._element
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('Stack is empty')
# the last item in the list
return self._data[-1]
def delete_last(self):
"""
Remove and return the element from the back of the deque.
Raise Empty exception if the deque is empty.
"""
# after header
if self.is_empty():
raise Empty('Deque is empty')
# use inherited method
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.
"""
# after header
if self.is_empty():
raise Empty('Deque is empty')
# use inherited method
return self._delete_node(self._header._next)
def pop(self):
"""
Remove and return the element from the top of the stack (i.e., LIFO).
Raise Empty exception if the stack is empty.
"""
if self.is_empty():
raise Empty('Stack is empty')
answer = self._head._element
# bypass the former top node
self._head = self._head._next
self._size -= 1
return answer
def remove_first(self):
"""
remove the node at the beginning.
"""
if self.is_empty():
raise Empty('LinkedList is empty')
node = self._head
self._head = self._head._next
self._size -= 1
element = node._element
node = None
return element
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 # help garbage collection
self._front = (self._front + 1) % len(self._data)
self._size -= 1
return answer
def _find_min(self):
"""
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.')
# put minimum item at the end
self._swap(0, len(self._data) - 1)
# and remove it from the list
item = self._data.pop()
# then fix new root
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')
answer = self._head._element
self._head = self._head._next
self._size -= 1
# special case as queue is empty
if self.is_empty():
# removed head had been the tail
self._tail = None
return answer
def remove_node(self, node):
if self.is_empty():
raise Empty('LinkedList is empty')
if self._size == 1:
self._head = _Node(None, None)
self._size -= 1
else:
if node._next is None:
self.remove_last()
else:
nxt = node._next
node._element = nxt._element
node._next = nxt._next
nxt = None
self._size -= 1
return node._element
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
# removing only element
if self._size == 1:
# queue becomes empty
self._tail = None
else:
# bypass the old head
self._tail._next = oldhead._next
self._size -= 1
return oldhead._next
def remove_last(self):
"""
remove the node at the end.
"""
if self.is_empty():
raise Empty('LinkedList is empty')
node = self._head
if self._size == 1:
self._head = _Node(None, None)
self._size -= 1
return node._element
while node._next is not None:
node = node._next
if node._next is None:
tail = node._next
self._size -= 1
node._next = None
element = tail._element
element = None
return element
