def first(self):
"""Return a reference to the element at the front of the deque.
Raise Empty exception if the deque is empty."""
if self.is_empty():
raise Empty('The deque 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('Deque is empty')
return self._delete_node(self._header._next)
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 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):
"""
Returns the lement at the front of the queue, without removing it.
Raises Empty exception if the queue is empty."""
if self.is_empty():
raise Empty('The queue is empty')
return self._data[self._front]
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')
return self._head._element # top of stack is at head of list
def pop(self):
"""
Removes and returns the element from the top of the stack.
Raises Empty exception if the stack is empty.
"""
if self.is_empty():
raise Empty('The stack is empty')
return self._data.pop()
def top(self):
"""
Returns the element at the top of the stack, without removing it.
Raises Empty exception if the stack is empty.
"""
if self.is_empty():
raise Empty('The stack is empty')
return self._data[-1]
def last(self):
"""Return a reference to the element at the back of the deque.
Raise Empty exception if the deque is empty."""
if self.is_empty():
raise Empty('The deque is empty')
last_in_line = (self._front + self._size - 1) % len(self._data)
return self._data[last_in_line]
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 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() # remove the minimum item from the list
self._downheap(0) # fix the new root
return (item._key, item._value)
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
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 pop(self):
"""Remove and return the last element in the array.
Raise Empty exception if the array is empty."""
if self._n == 0:
raise Empty('The array is empty')
answer = self._A[self._n - 1]
self._A[self._n - 1] = None # help garbage collection
self._n -= 1
if self._capacity // 4 > self._n: # shrink capacity if needed
self._resize(self._capacity // 2)
return answer
def delete_last(self):
"""Delete an element from the back of the deque.
Raise Empty exception if the deque is empty."""
if self.is_empty():
raise Empty('The deque is empty.')
last_in_line = (self._front + self._size - 1) % len(self._data)
result = self._data[last_in_line]
self._data[last_in_line] = None
self._size -= 1
return result
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():
self._tail = None
return answer
def delete_first(self):
"""Delete an element from the front of the deque.
Raise Empty exception if the deque is empty."""
if self.is_empty():
raise Empty('The deque is empty.')
result = self._data[self._front] # Save result to return later
self._data[self._front] = None
self._front = (self._front + 1) % len(self._data)
self._size -= 1
return result
def dequeue(self):
"""
Removes and returns the element in front of the queue.
Raises Empty exception if the queue is empty."""
if self.is_empty():
raise Empty('The queue is empty')
result = self._data[self._front]
self._data[self._front] = None
self._front = (self._front + 1) % len(self._data)
self._size -= 1
return result
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 first(self):
"""Return (but do not remove) the element at the front of the queue."""
if self.is_empty():
raise Empty('Queue is empty')
return self._head._element
def remove_min(self):
"""Remove and return (k, v) tuple with minimum key from the priority queue."""
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')
return self._trailer._prev._element # the item before the trailer sentinel
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')
return self._header._next._element # the item after the header sentinel