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DLLRemoveLastElement.py
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105 lines (93 loc) · 2.38 KB
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class _Node:
__slots__ = '_element', '_next', '_prev'
def __init__(self, element, next, prev):
self._element = element
self._next = next
self._prev = prev
class DoublyLinkedList:
def __init__(self):
self._head = None
self._tail = None
self._size = 0
def __len__(self):
return self._size
def isempty(self):
return self._size == 0
def addlast(self, e):
newest = _Node(e, None, None)
if self.isempty():
self._head = newest
self._tail = newest
else:
self._tail._next = newest
newest._prev = self._tail
self._tail = newest
self._size += 1
def addfirst(self, e):
newest = _Node(e, None, None)
if self.isempty():
self._head = newest
self._tail = newest
else:
newest._next = self._head
self._head._prev = newest
self._head = newest
self._size += 1
def addany(self, e, position):
newest = _Node(e, None, None)
p = self._head
i = 1
while i < position-1:
p = p._next
i = i + 1
newest._next = p._next
p._next = newest
p._next._prev = newest
newest._prev = p
self._size += 1
def removefirst(self):
if self.isempty():
print('List is empty')
return
e = self._head._element
self._head = self._head._next
self._size -= 1
if self.isempty():
self._tail = None
else:
self._head._prev = None
return e
def removelast(self):
if self.isempty():
print('List is empty')
return
e = self._tail._element
self._tail = self._tail._prev
self._tail._next = None
self._size -= 1
return e
def display(self):
p = self._head
while p:
print(p._element,end=' --> ')
p = p._next
print()
def displayrev(self):
p = self._tail
while p:
print(p._element,end=' <-- ')
p = p._prev
print()
L = DoublyLinkedList()
L.addlast(7)
L.addlast(4)
L.addlast(12)
L.addlast(8)
L.addlast(3)
L.display()
print('Size:',len(L))
ele = L.removelast()
L.display()
print('Size:',len(L))
print('Removed Element:',ele)
L.displayrev()