public class DeleteMid {
//Represents the node of list.
public class Node{
int data;
Node next;
public Node(int data) {
this.data = data;
}
}
public int size;
//Declaring head and tail pointer as null.
public Node head = null;
public Node tail = null;
//This function will add the new node at the end of the list.
public void add(int data){
//Create new node
Node newNode = new Node(data);
//Checks if the list is empty.
if(head == null) {
//If list is empty, both head and tail would point to new node.
head = newNode;
tail = newNode;
newNode.next = head;
}
else {
//tail will point to new node.
tail.next = newNode;
//New node will become new tail.
tail = newNode;
//Since, it is circular linked list tail will point to head.
tail.next = head;
}
//Counts the number of nodes in list
size++;
}
//Deletes node from the middle of the list
public void deleteMid() {
Node current, temp;
//Checks whether list is empty
if(head == null) {
return;
}
else {
//Store the mid position of the list
int count = (size % 2 == 0) ? (size/2) : ((size+1)/2);
//Checks whether head is equal to tail or not, if yes then list has only one node.
if( head != tail ) {
//Initially temp will point to head;
temp = head;
current = null;
//Current will point to node previous to temp
//If temp is pointing to node 2 then current will points to node 1.
for(int i = 0; i < count-1; i++){
current = temp;
temp = temp.next;
}
if(current != null) {
//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 = null;
}
//Current points to null then head and tail will point to node next to temp.
else {
head = tail = temp.next;
tail.next = head;
//Delete temp;
temp = null;
}
}
//If the list contains only one element
//then it will remove it and both head and tail will point to null
else {
head = tail = null;
}
}
size--;
}
//Displays all the nodes in the list
public void display() {
Node current = head;
if(head == null) {
System.out.println("List is empty");
}
else {
do{
//Prints each node by incrementing pointer.
System.out.print(" "+ current.data);
current = current.next;
}while(current != head);
System.out.println();
}
}
public static void main(String[] args) {
DeleteMid cl = new DeleteMid();
//Adds data to the list
cl.add(1);
cl.add(2);
cl.add(3);
cl.add(4);
//Printing original list
System.out.println("Original List: ");
cl.display();
while(cl.head != null) {
cl.deleteMid();
//Printing updated list
System.out.println("Updated List: ");
cl.display();
}
}
}
Original List:
1 2 3 4
Updated List:
1 3 4
Updated List:
1 4
Updated List:
4
Updated List:
List is empty
List is empty
". If the list is not empty, we will calculate the size of the list and then divide it by 2 to get the mid-point of the list. We maintain two pointers temp and current. Current will point to the previous node of temp. We will iterate through the list until mid-point is reached then the current will point to the middle node. We delete middle node such that current's next will be temp's next node.node
is 2. To remove C from the list, we will iterate through the list till mid-point. Now current will point to B and temp will point to C. C will be removed when B will point to D.deleteMid()
and display()
.deleteMid()
will delete the node from the middle of the list :a. display()
will show all the nodes present in the list.