def addToTail(self, value):
newNode = Node(value)
if not self.tail:
self.head = newNode
else:
self.tail.next = newNode
newNode.prev = self.tail
self.items.append(newNode)
self.tail = newNode
def addToHead(self, value):
newNode = Node(value)
if not self.head:
self.tail = newNode
else:
self.head.prev = newNode
newNode.next = self.head
self.items.insert(0, newNode)
self.head = newNode
def insertAtIndex(self, index, value):
if index > len(self.items) - 1:
return False
if index == 0:
return self.addToHead(value)
if index == len(self.items) - 1:
return self.addToTail(value)
new_node = Node(value)
before_node = self.items[index - 1]
after_node = self.items[index]
before_node.next = new_node
new_node.prev = before_node
after_node.prev = new_node
new_node.next = after_node
self.items.insert(index, new_node)
def add(self, item):
if self.head == None:
self.head = Node(item)
else:
temp = Node(item)
temp.set_next(self.head)
self.head.set_previous(temp)
self.head = temp
def append(self, item):
if self.head == None:
self.head = Node(item)
else:
current = self.head
while current.get_next() != None:
current = current.get_next()
temp = Node(item)
current.set_next(temp)
temp.set_previous(current)
def insert_after(self, item, x):
if self.head == None:
print("List is empty")
else:
current = self.head
found = False
while current != Nonde and not found:
if current.get_item() == x:
found = True
else:
current = current.get_next()
if found == False:
print("item is not in the list")
else:
temp = Node(item)
temp.set_next(current.get_next())
temp.set_previous(current)
if current.get_next() != None:
current.get_next().set_previous(temp)
current.set_next(temp)
class DList:
def __init__(self):
self.head = None
def is_empty(self):
return self.head == None
def add(self, item):
if self.head == None:
self.head = Node(item)
else:
temp = Node(item)
temp.set_next(self.head)
self.head.set_previous(temp)
self.head = temp
def append(self, item):
if self.head == None:
self.head = Node(item)
else:
current = self.head
while current.get_next() != None:
current = current.get_next()
temp = Node(item)
current.set_next(temp)
temp.set_previous(current)
def insert_after(self, item, x):
if self.head == None:
print("List is empty")
else:
current = self.head
found = False
while current != Nonde and not found:
if current.get_item() == x:
found = True
else:
current = current.get_next()
if found == False:
print("item is not in the list")
else:
temp = Node(item)
temp.set_next(current.get_next())
temp.set_previous(current)
if current.get_next() != None:
current.get_next().set_previous(temp)
current.set_next(temp)
def insert_before(self, item, x):
if self.head == None:
print("List is empty")
else:
current = self.head
found = False
while current != Nonde and not found:
if current.get_item() == x:
found = True
else:
current = current.get_next()
if found == False:
print("item is not in the list")
else:
temp = Node(item)
temp.set_next(current)
temp.set_previous(current.get_previous())
if current.get_previous() != None:
current.get_previous().set_next(temp)
else:
self.head = temp
current.set_previous(temp)
def pop_first(self):
if self.head == None:
print("List is empty")
else:
if self.head.get_next() == None:
self.head = None
else:
self.head = self.head.get_next()
self.head.set_previous(None)
def pop_last(self):
if self.head == None:
print("List is empty")
else:
if self.head.get_next() == None:
self.head = None
else:
current = self.head
while current.get_next() != None:
current = current.get_next()
current.get_previous().set_next(None)
def delete(self, item):
if self.head.get_item() == item:
self.head = self.head.get_next()
self.head.set_previous(None)
else:
current = self.head
found = False
while not found:
if current.get_item() == item:
found = True
else:
current = current.get_next()
if current.get_next() != None:
current.get_previous().set_next(current.get_next())
current.get_next().set_previous(current.get_previous())
else:
current.get_previous().set_next(None)
def search(self, item):
current = self.head
found = False
while current != None and not found:
if current.get_item() == item:
found = True
else:
current = current.get_next()
return found
def size(self):
current = self.head
count = 0
while current != None:
count = count + 1
current = current.get_next()
return count