def push(self, new_data):
new_node = Node(data = new_data)
new_node.prev = None # at the beginning
new_node.next = self.head
if self.head is not None:
self.head.prev = new_node
self.head = new_node
def insert(self, index, data):
"""
Purpose: Insert new node at given index position
:param index: node index to insert
:param data: new node data
:return:
"""
if index == 0 or self.head is None:
self.push_front(data=data)
return
if index >= self.__len__():
self.push_back(data=data)
return
n = Node(data=data)
i = 0
current = self.head
prev = self.head
while current:
if index == i:
prev.next = n
n.next = current
self.size += 1
return
i += 1
prev = current
current = current.next
def insert_before(self, next_node, new_data):
if next_node is None:
print("Error: given next_node is None")
return
new_node = Node(data = new_data)
new_node.next = next_node
new_node.prev = next_node.prev
if new_node.prev is not None: # if new_node.prev (next_node.prev) is None it means we are at the beginning of the list
new_node.prev.next = new_node
next_node.prev = new_node
def insert_after(self, prev_node, new_data):
if prev_node is None:
print("Error: given prev_node is None")
return
new_node = Node(data = new_data)
new_node.prev = prev_node
new_node.next = prev_node.next
if new_node.next is not None: # if new_node.next (prev_node.next) is None it means we are at the end of the list
new_node.next.prev = new_node
prev_node.next = new_node
def add_to_head(self, item):
new_node = Node()
new_node.item = item
if not self.head:
self.head = new_node
else:
old_head = self.head
new_node.next = old_head
self.head = new_node
def add_to_head(self, item):
new_node = Node()
new_node.item = item
if not self.head:
self.head = new_node
else:
old_head = self.head
new_node.next = old_head
self.head = new_node
def append(self, new_data):
new_node = Node(data = new_data)
new_node.next = None # at the last
last = self.tail
# if list is empty then this is the first node
if last is None:
new_node.prev = None
self.head = new_node
return
last.next = new_node
new_node.prev = last
def insert_at(self, index, value):
'''
Inserts a value at the given position.
index -- the position as an int.
value -- an object.
'''
if not isinstance(index, int):
raise TypeError("index is not of type int")
if index < 0 or index > self.size:
raise LookupError("index out of bounds")
new_node = Node()
new_node.data = value
if self.head is None:
self.head = new_node
self.tail = new_node
self.size = 1
return
if index == 0:
new_node.next = self.head
self.head.previous = new_node
self.head = new_node
self.size = 1
else:
current_node = self.head
for i in range(index-1):
current_node = current_node.next
new_node.previous = current_node
new_node.next = current_node.next
current_node.next = new_node
if(new_node.next is None):
self.tail = new_node
self.size = 1
def push_front(self, data):
"""
Purpose: Push (add) node to front of SLL
:param data: new node data
:return:
"""
n = Node(data=data)
if self.head is None:
self.head = n
self.size += 1
return
old_head = self.head
self.head = n
n.next = old_head
self.size += 1
#
# return dummy
#
n1 = Node(1, None, None, None)
n2 = Node(2, n1, None, None)
n3 = Node(3, n2, None, None)
n4 = Node(4, n3, None, None)
n5 = Node(5, n4, None, None)
n6 = Node(6, n5, None, None)
n7 = Node(7, n6, None, None)
n8 = Node(8, n7, None, None)
n9 = Node(9, n8, None, None)
n10 = Node(10, n9, None, None)
n11 = Node(11, n10, None, None)
n12 = Node(12, n11, None, None)
n1.next = n2
n2.next = n3
n3.next = n4
n4.next = n5
n5.next = n6
n7.next = n8
n8.next = n9
n9.next = n10
n11.next = n12
n3.child = n7
n8.child = n11
head = Solution().flatten(n1)