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JAVA Program for Deletion from Beginning in a Doubly Linked List
JAVA Program to Delete a Node from the Beginning
Over here in this program we will create a linked list and add a node at the end of doubly linked list. To insert a new node at the end of a linked list we have to check that the list is empty or not. If the list is empty both head and tail points towards the newly added node. If it is not empty, in such case add a new node at the end and make sure that tail points towards the newly added node.
Steps to be followed while Inserting a Node at the Beginning of a Doubly Linked List
- Check for the presence of Node in the List, if there exists some Nodes, Continue.
- Now, to Delete a node from the end of the Doubly Linked List, we’ll have to create and redirect multiple links in the Linked List.
- Foremost, the link between the First Node and the head and the link between the Previous Pointer of the First Node and the null will also be broken.
- Now Since the Second Node is going to be the First Node of the Linked List. So, the Head will now Point to the address of the Second Node.
- Then the Previous Pointer of the Second Node will now point to Null.
Example:
If we have a list (10 –> 20 –> 30 –> 40) and we have to add a new node which is 50. So after adding new node. Updated Linked list will be (10 –> 20 –> 30 –>40 –> 50) . We will be learning more about the whole process in the explanation below.
Algorithm to be used for Deletion from the Beginning of a Doubly Linked List
- IF(HEAD == NULL)
- RETURN
- ELSE IF(HEAD != TAIL)
- TAIL = TAIL.PREV
- TAIL.NEXT = NULL
- ELSE
- HEAD = TAIL = NULL
Java Program for Deletion from the Beginning of a Doubly Linked List
Method 1
Method 2
Method 1
Run
import java.lang.*;
class DoublyLinkedList
{
Node head;
// not using parameterized constructor would by default
// force head instance to become null
// Node head = null; // can also do this, but not required
// Node Class
class Node
{
int data;
Node next, prev;
Node (int x) // parameterized constructor
{
data = x;
next = null;
prev = null;
}
}
public void insertBeginning (int data)
{
// Creating newNode memory & assigning data value
Node freshNode = new Node (data);
freshNode.next = head;
freshNode.prev = null;
// if DLL had already >=1 nodes
if (head != null)
head.prev = freshNode;
// changing head to this
head = freshNode;
}
// function for deleting first node
public void deleteInitial ()
{
if (head == null)
{
System.out.println ("List is empty");
return;
}
else
{
//testing for the presence of a single node in the list, If not, Then head and tail will be re-directed
if (head != null)
{
head = head.next;
}
//if only one node exist both head and tail will be redirected to null
else
{
head = null;
}
}
}
void printList ()
{
//Node current will point to head
Node curr = head;
if (head == null)
{
System.out.println ("List is empty");
return;
}
while (curr != null)
{
//Prints each node by increasing order of the pointer
System.out.print (curr.data + " ");
curr = curr.next;
}
System.out.println ();
}
}
class Main
{
public static void main (String args[])
{
DoublyLinkedList doublylist = new DoublyLinkedList ();
doublylist.insertBeginning (3);
doublylist.insertBeginning (2);
doublylist.insertBeginning (1);
doublylist.insertBeginning (4);
doublylist.insertBeginning (7);
System.out.println ("List before deletion : ");
doublylist.printList ();
doublylist.deleteInitial ();
System.out.println ("List after deletion : ");
doublylist.printList ();
}
}
Output
List before deletion : 7 4 1 2 3 List after deletion : 4 1 2 3
Method 2
Run
import java.lang.*;
// Node Class
class Node {
int data;
Node next, prev;
Node(int x) // parameterized constructor
{
data = x;
next = null;
prev = null;
}
}
class Main
{
static Node insertBeginning(Node head, int data)
{
// Creating newNode memory & assigning data value
Node newNode = new Node(data);
newNode.next = head;
newNode.prev = null;
// if DLL had already >=1 nodes
if(head !=null)
head.prev = newNode;
// changing head to this
head = newNode;
return head;
}
// function for deleting first node
static Node deleteInitial ( Node head)
{
if (head == null)
{
System.out.println ("List is empty");
return head;
}
else
{
//testing for the presence of a single node in the list, If not, Then head and tail will be re-directed
if (head != null)
{
head = head.next;
}
//if only one node exist both head and tail will be redirected to null
else
{
head = null;
}
}
return head;
}
static void printList (Node head)
{
//Node current will point to head
Node curr = head;
if (head == null)
{
System.out.println ("List is empty");
return;
}
while (curr != null)
{
//Prints each node by increasing order of the pointer
System.out.print (curr.data + " ");
curr = curr.next;
}
System.out.println ();
}
// required for insertAfterPosition() method
static int getLength(Node node){
int size=0;
// traverse to the last node each time incrementing the size
while(node!=null)
{
node = node.next;
size++;
}
return size;
}
public static void main(String args[])
{
Node head = null;
head = insertBeginning(head,3);
head = insertBeginning(head,2);
head = insertBeginning(head,1);
head = insertBeginning(head,4);
head = insertBeginning(head,7);
System.out.println ("List before deletion : ");
printList (head);
head = deleteInitial (head);
System.out.println ("List after deletion : ");
printList (head);
}
}
Output
List before deletion : 7 4 1 2 3 List after deletion : 4 1 2 3
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Doubly Linked List
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