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 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')
return self._head._element # top of stack is at head of list
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._head._element # front aligned with head of list
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) # use inherited method
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) # use inherited method
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 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 last(self):
"""Return (but do not remove) the element at the back 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)
return self._data[back]
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 _find_min(self): # nonpublic utility
"""Return Position of item with minimum key."""
if self.is_empty(): # is_empty inherited from base class
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 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
self._head = self._head._next # bypass the former top node
self._size -= 1
return answer
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) # put minimum item at the end
item = self._data.pop() # and remove it from the list;
self._downheap(0) # then fix new root
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
if self.is_empty(): # special case as queue is empty
self._tail = None # removed head had been the tail
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')
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)
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: # removing only element
self._tail = None # queue becomes empty
else:
self._tail._next = oldhead._next # bypass the old head
self._size -= 1
return oldhead._element
def delete_last(self):
"""Remove and return the last 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)
answer = self._data[back]
self._data[back] = None # help garbage collection
self._size -= 1
if 0 < self._size < len(self._data) // 4:
self._resize(len(self._data) // 2)
return answer
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')
return self._trailer._prev._element # real item just before trailer
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)
