Python program to delete a node from the middle of the Circular Linked List
#Represents the node of list.
class Node:
def __init__(self,data):
self.data = data;
self.next = None;
class CreateList:
#Declaring head and tail pointer as null.
def __init__(self):
self.head = Node(None);
self.tail = Node(None);
self.head.next = self.tail;
self.tail.next = self.head;
self.size = 0;
#This function will add the new node at the end of the list.
def add(self,data):
newNode = Node(data);
#Checks if the list is empty.
if self.head.data is None:
#If list is empty, both head and tail would point to new node.
self.head = newNode;
self.tail = newNode;
newNode.next = self.head;
else:
#tail will point to new node.
self.tail.next = newNode;
#New node will become new tail.
self.tail = newNode;
#Since, it is circular linked list tail will point to head.
self.tail.next = self.head;
#Size will count the number of nodes in the list
self.size = int(self.size)+1;
#Deletes node from the middle of the list
def deleteMid(self):
#Checks whether list is empty
if(self.head == None):
return;
else:
#Store the mid position of the list
count = (self.size//2) if (self.size % 2 == 0) else ((self.size+1)//2);
#Checks whether head is equal to tail or not, if yes then list has only one node.
if( self.head != self.tail ):
#Initially temp will point to head;
temp = self.head;
current = None;
#Current will point to node previous to temp
#If temp is pointing to node 2 then current will points to node 1.
for i in range(0, count-1):
current = temp;
temp = temp.next;
if(current != None):
#temp is the middle that needs to be removed.
#So, current node will point to node next to temp by skipping temp.
current.next = temp.next;
#Delete temp;
temp = None;
#Current points to null then head and tail will point to node next to temp.
else:
self.head = self.tail = temp.next;
self.tail.next = self.head;
#Delete temp;
temp = None;
#If the list contains only one element
#then it will remove it and both head and tail will point to null
else:
self.head = self.tail = None;
self.size = self.size - 1;
#Displays all the nodes in the list
def display(self):
current = self.head;
if self.head is None:
print("List is empty");
return;
else:
#Prints each node by incrementing pointer.
print(current.data),
while(current.next != self.head):
current = current.next;
print(current.data),
print("\n");
class CircularLinkedList:
cl = CreateList();
#Adds data to the list
cl.add(1);
cl.add(2);
cl.add(3);
cl.add(4);
#Printing original list
print("Original List:");
cl.display();
while(cl.head != None):
cl.deleteMid();
#Printing updated list
print("Updated List:");
cl.display();
Output:
Original List:
1 2 3 4
Updated List:
1 3 4
Updated List:
1 4
Updated List:
4
Updated List:
List is empty
