CODEWITHSUNDEEP
javalinked-list
Robert
Robert

Reputation: 143

Insertion at index of LinkedList

Hi I have this method to insert an element at any index of the LinkedList, however, the new element is not showing in the output, what did i miss thanks! I have showed partial code below, any help is greatly appreciated!

public class LinkedList<E extends Comparable<E>> implements Iterable<E>
{
    // instance data members of list
    private Node head; // reference to the first node
    private int N;     // number of elements stored in the list

    private class Node
    {
        // instance data members of Node
        public E item;
        public Node next;

        // constructors for Node
        public Node()
        {
            item = null;  next = null;
        }

        public Node(E e, Node ptr)
        {
            item = e;  next = ptr;
        }
    }// end class Node

    public void insertAfter(int k, E e){
        if (k < 0 || k >= size()){
            throw new IndexOutOfBoundsException();}
        Node temp=new Node();
        temp.item=e;
        int index=k-1;
        Node current=head;
        for (int i=0; i<=N; N++){
            if (i==index){
                temp.next=current.next;
                current.next=temp;
            }
        }
        ++N;  
    }

Upvotes: 0

Views: 910

Answers (2)

Veselin Davidov
Veselin Davidov

Reputation: 7071

You are not moving the current element throught the list. You loop the integer indexes but don't move the pointer to the current node. So in the loop current is always the head of the linked list. You need to make it like that:

for (int i=0; i<=N; N++)
        if (i==index){
            temp.next=current.next;
            current.next=temp;
        }else{
         current=current.next;
       }

This way when you add the element you will be in the proper position. Otherwise you will ways insert it in the first position.

Upvotes: 1

Steve Chaloner
Steve Chaloner

Reputation: 8202

It looks like you're incrementing an instance variable N

Try this instead

public void insertAfter(int k, E e){
    if (k < 0 || k >= size()){
        throw new IndexOutOfBoundsException();}
    Node temp=new Node();
    temp.item=e;
    int index=k-1;
    Node current=head;
    for (int i=0; current != null && i<N; i++){
        if (i==index){
            temp.next=current.next;
            current.next=temp;
        } else {
            current = current.next;
        }
    }
    ++N;  
}

Don't forget that if you insert a node at position 0, you need to update what head references.

Upvotes: 1

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