linked list python example
class ListNode:
def __init__(self, value, prev=None, next=None):
self.prev = prev
self.value = value
self.next = next
class DoublyLinkedList:
def __init__(self, node=None):
self.head = node
self.tail = node
self.length = 1 if node is not None else 0
def __len__(self):
return self.length
def add_to_head(self, value):
new_node = ListNode(value, None, None)
self.length += 1
if not self.head and not self.tail:
self.head = new_node
self.tail = new_node
else:
new_node.next = self.head
self.head.prev = new_node
self.head = new_node
def remove_from_head(self):
value = self.head.value
self.delete(self.head)
return value
def add_to_tail(self, value):
new_node = ListNode(value, None, None)
self.length += 1
if not self.tail and not self.head:
self.tail = new_node
self.head = new_node
else:
new_node.prev = self.tail
self.tail.next = new_node
self.tail = new_node
def remove_from_tail(self):
value = self.tail.value
self.delete(self.tail)
return value
def move_to_front(self, node):
if node is self.head:
return
value = node.value
if node is self.tail:
self.remove_from_tail()
else:
node.delete()
self.length -= 1
self.add_to_head(value)
def move_to_end(self, node):
if node is self.tail:
return
value = node.value
if node is self.head:
self.remove_from_head()
self.add_to_tail(value)
else:
node.delete()
self.length -= 1
self.add_to_tail(value)
def delete(self, node):
self.length -= 1
if not self.head and not self.tail:
return
if self.head == self.tail:
self.head = None
self.tail = None
elif self.head == node:
self.head = node.next
node.delete()
elif self.tail == node:
self.tail = node.prev
node.delete()
else:
node.delete()
def get_max(self):
if not self.head:
return None
max_val = self.head.value
current = self.head
while current:
if current.value > max_val:
max_val = current.value
current = current.next
return max_val
class Node:
def __init__(self, data=None):
self.data = data
self.next = None
class SLinkedList:
def __init__(self):
self.head = None
def Atbegining(self, data_in):
NewNode = Node(data_in)
NewNode.next = self.head
self.head = NewNode
# Function to remove node
def RemoveNode(self, Removekey):
HeadVal = self.head
if (HeadVal is not None):
if (HeadVal.data == Removekey):
self.head = HeadVal.next
HeadVal = None
return
while (HeadVal is not None):
if HeadVal.data == Removekey:
break
prev = HeadVal
HeadVal = HeadVal.next
if (HeadVal == None):
return
prev.next = HeadVal.next
HeadVal = None
def LListprint(self):
printval = self.head
while (printval):
print(printval.data),
printval = printval.next
llist = SLinkedList()
llist.Atbegining("Mon")
llist.Atbegining("Tue")
llist.Atbegining("Wed")
llist.Atbegining("Thu")
llist.RemoveNode("Tue")
llist.LListprint()class Node:
def __init__(self, data = None, next_node = None):
self.data = data
self.nextNode = next_node
def get_data(self):
return self.data
def set_data(self, data):
self.data = data
def get_nextNode(self):
return self.nextNode
def set_nextNode(self, nextNode):
self.nextNode = nextNode
class LinkedList:
def __init__(self, head = None):
self.head = head
def add_Node(self, data):
# if empty
if self.head == None:
self.head = Node(data)
# not empty
else:
curr_Node = self.head
# if node added is at the start
if data < curr_Node.get_data():
self.head = Node(data, curr_Node)
# not at start
else:
while data > curr_Node.get_data() and curr_Node.get_nextNode() != None:
prev_Node = curr_Node
curr_Node = curr_Node.get_nextNode()
# if node added is at the middle
if data < curr_Node.get_data():
prev_Node.set_nextNode(Node(data, curr_Node))
# if node added is at the last
elif data > curr_Node.get_data() and curr_Node.get_nextNode() == None:
curr_Node.set_nextNode(Node(data))
def search(self, data):
curr_Node = self.head
while curr_Node != None:
if data == curr_Node.get_data():
return True
else:
curr_Node = curr_Node.get_nextNode()
return False
def delete_Node(self, data):
if self.search(data):
# if data is found
curr_Node = self.head
#if node to be deleted is the first node
if curr_Node.get_data() == data:
self.head = curr_Node.get_nextNode()
else:
while curr_Node.get_data() != data:
prev_Node = curr_Node
curr_Node = curr_Node.get_nextNode()
#node to be deleted is middle
if curr_Node.get_nextNode() != None:
prev_Node.set_nextNode(curr_Node.get_nextNode())
# node to be deleted is at the end
elif curr_Node.get_nextNode() == None:
prev_Node.set_nextNode(None)
else:
return "Not found."
def return_as_lst(self):
lst = []
curr_Node = self.head
while curr_Node != None:
lst.append(curr_Node.get_data())
curr_Node = curr_Node.get_nextNode()
return lst
def size(self):
curr_Node = self.head
count = 0
while curr_Node:
count += 1
curr_Node = curr_Node.get_nextNode()
return count
## TEST CASES #
test1 = LinkedList()
test2 = LinkedList()
test1.add_Node(20)
test1.add_Node(15)
test1.add_Node(13)
test1.add_Node(14)
test1.delete_Node(17)
print(test1.return_as_lst())
print(test2.size())
# A simple Python program to introduce a linked list
# Node class
class Node:
# Function to initialise the node object
def __init__(self, data):
self.data = data # Assign data
self.next = None # Initialize next as null
# Linked List class contains a Node object
class LinkedList:
# Function to initialize head
def __init__(self):
self.head = None
# Code execution starts here
if __name__=='__main__':
# Start with the empty list
llist = LinkedList()
llist.head = Node(1)
second = Node(2)
third = Node(3)
'''
Three nodes have been created.
We have references to these three blocks as head,
second and third
llist.head second third
| | |
| | |
+----+------+ +----+------+ +----+------+
| 1 | None | | 2 | None | | 3 | None |
+----+------+ +----+------+ +----+------+
'''
llist.head.next = second; # Link first node with second
'''
Now next of first Node refers to second. So they
both are linked.
llist.head second third
| | |
| | |
+----+------+ +----+------+ +----+------+
| 1 | o-------->| 2 | null | | 3 | null |
+----+------+ +----+------+ +----+------+
'''
second.next = third; # Link second node with the third node
'''
Now next of second Node refers to third. So all three
nodes are linked.
llist.head second third
| | |
| | |
+----+------+ +----+------+ +----+------+
| 1 | o-------->| 2 | o-------->| 3 | null |
+----+------+ +----+------+ +----+------+
'''
class LinkedList:
class _Node:
__slots__ = '_element', '_next'
def __init__(self, element, next):
self._element = element
self._next = next
def __init__(self):
self._head = None
self._tail = None
self._size = 0
def __len__(self):
return self._size
def is_empty(self):
return self._size == 0
def add_first(self, e):
newest = self._Node(e, None)
if self.is_empty():
self._head = newest
self._tail = newest
else:
newest._next = self._head
self._head = newest
self._size += 1
def add_last(self, e):
newest = self._Node(e, None)
if self.is_empty():
self._head = newest
self._tail = newest
else:
self._tail._next = newest
self._tail = newest
self._size += 1
def add_any(self, e, pos):
newest = self._Node(e, None)
thead = self._head
i = 1
while i < pos:
thead = thead._next
i += 1
newest._next = thead._next
thead._next = newest
self._size += 1
def remove_first(self):
if self.is_empty():
raise Empty('Linked List empty')
value = self._head._element
self._head = self._head._next
self._size -= 1
if self.is_empty():
self._tail = None
return value
def remove_last(self):
if self.is_empty():
raise Empty('Linked list is empty')
thead = self._head
i = 0
while i < len(self) - 2:
thead = thead._next
i += 1
self._tail = thead
thead = thead._next
value = thead._element
self._tail._next = None
self._size -= 1
return value
def remove_any(self):
if self.is_empty():
raise Empty('linked list is empty')
thread = self._head
i = 1
while i < pos - 1:
thead = thead._next
i += 1
value = thead._next._element
thead._next = thead._next._next
self._size -= 1
return value
def display(self):
thead = self._head
while thead:
print(thead._element, end='-->')
thead = thead._next
print()
class Empty(Exception):
pass
