Implementing a method to delete last node of a linked list

Question

I am trying to delete the last node in LinkedList. For the input: 1, 2, 3 Output should be: 1, 2

I am able to delete the node, but is there a better/more efficient way of doing so?

Please check the removeLastNode() method.

public class MyLinkedList {

Node head;
Node tail;

public void add(int number){

    Node node=new Node();
    node.setNumber(number);

    if(head==null){
        head=node;
        tail=node;  
    }
    else{
        tail.next=node;
        tail=node;          
    }

}



public void removeLastNode(){   
    Node temp=head;
    Node head1=null;
    Node tail1=null;


    while(temp.next!=null){

        Node node=new Node();
        node.number=temp.number;
        if(head1==null){
            head1=node;
            tail1=node; 
        }
        else{
            tail1.next=node;
            tail1=node;         
        }
        if(temp.next.next==null){               
            temp.next=null;
            break;
        }

        temp=temp.next;

    }
    head=head1;


}


@Override
public String toString(){
    while(head!=null){
        System.out.print(head.getNumber()+" ");
        head=head.getNext();
    }
    return "";
}

public static void main(String ar[]){

    MyLinkedList list=new MyLinkedList();
    list.add(1);
    list.add(2);
    list.add(3);
    list.removeLastNode();

    System.out.println(list);
}




public class Node{

    Node next;
    int number;
    public Node getNext() {
        return next;
    }
    public void setNext(Node next) {
        this.next = next;
    }
    public int getNumber() {
        return number;
    }
    public void setNumber(int number) {
        this.number = number;
    }


}

}

You can use a double linked list where each node stored the address to the previous and next nodes — Slimu
– Slimu, Commented Jul 14, 2016 at 10:32
Be aware that Javas class LinkedList implements a Doubly-linked list by default, it is not a regular linked list! Thus you already may be good to go with Java's LinkedList. Or, if you need to implement it by yourself, you can look up how to do it there. — Zabuzard
– Zabuzard, Commented Jul 14, 2016 at 10:36

Joop Eggen · Accepted Answer · 2016-07-14 11:29:58Z

1

Use that tail is the last node.

public void removeLastNode() {
    if (head == null) {
        throw new IllegalStateException();
    }
    if (head == tail) {
        head = null;
        tail = null;
    } else {
        Node current = head;
        while (current.next != tail) {
            current = current.next;
        }
        current.next = null;
        tail = current;
    }
}

answered Jul 14, 2016 at 11:29

Joop Eggen

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Comments

Dominik Reinert · Accepted Answer · 2016-07-14 10:32:38Z

1

Add a Node previousattribute to the Node and a Node last to LinkedList to get a DoubleLinkedList.

Then you can do something like

Node temp = List.getLast().getPrevious(); //returns the second last item
List.removeLast();    //sets the last item to null
List.setLast(temp);   //sets the last item to the second last item
List.getLast().setNext(null);

answered Jul 14, 2016 at 10:32

Dominik Reinert

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Comments

sumit katiyar · Accepted Answer · 2019-04-03 10:09:07Z

0

Yes You can delete last node from linked list by tracking previous node.

public int deleteAtLast() {
    if (head == null) {
        return 0;
    } else {
        Node prevoursNode = null;
        Node n = head;
        while (n.next != null) {
            prevoursNode=n;
            n = n.next;
        }
        int data = n.data;
        prevoursNode.next=null;
        return data;
    }

}

answered Apr 3, 2019 at 10:09

sumit katiyar

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