Question

Write an application and perform the following:(NO USER INPUT)

-Create at least three classes such as:

1. listnode- for data and link, constructors

2. Singlelinkedlist-for method definition

3. linkedlist-for objects

-Insert a node at tail/end in a linked list.

-and display all the nodes in the list.

-Delete a node at a position in the list

Note: Add these methods in the same application which we have done in the class.

this is what we've done in the class:

class listnode{
int data;//first part of the node(data)
listnode link;//second part of the node(address)
listnode()
{
data=0;
link=null;
}
listnode(int d,listnode l)//10|null
{
data=d;
link=l;
}
}
class singlelinklist{
void display(listnodes head){
listnodes current=head;
while(current.link!=null){
System.out.print(current.data+"-->");
current=current.link;
}
System.out.print(current.data);
  
}
public listnodes insert(listnodes head,int data)
{
//create new node
listnodes newnode=new listnodes(data,null);
//link the newnode to the head node
newnode.link=head;
//make newnode the first node
head=newnode;
return head;//return the first node
}
//insert at a position(after or before a node)
public listnodes InsertAtPostion(listnodes head,int data,int position){
listnodes newnode=new listnodes(data,null);   
listnodes previous=head;
int count=1;
while(count<=position-1){//(count<position)
previous=previous.link;
count++;
}
// listnodess current=previous.link;
listnodes current=previous;
current=previous.link;
newnode.link=current;
previous.link=newnode;
return head;


}
public listnodes deletefirst(listnodes head){
listnodes temp=head;//rename
head=head.link;//move head
temp.link=null;//temp alone
return temp;
}
public listnodes deletelast(listnodes head){

if(head==null){
return head;
}
listnodes last=head;
listnodes previoustolast=head;
while(last.link!=null){
previoustolast=last;
last=last.link;
}
previoustolast.link=null;
return last;
}
public int length(listnodes head){
listnodes curr=head;
int c=0;
while(curr!=null){
c++;
curr=curr.link;
  
}
return c;
}
public boolean find(listnodes head,int searchkey){
listnodes curr=head;
while(curr!=null){
if(curr.data==searchkey)
{
return true;
}
curr=curr.link;
}
return false;
}
}

public class Link {
public static void main(String[] args) {
//craete first node
listnodes head=new listnodes(10,null);
//create an object of class where all the methods are   
singlelinklist sl=new singlelinklist();
//insert at postion
sl.InsertAtPostion(head, 30, 1);

//insert at front
listnodes newhead=sl.insert(head,20);
sl.display(newhead);

//delete last
System.out.println(" ");
System.out.println("Delete a node at end");
listnodes l=sl.deletelast(head);
sl.display(l);
System.out.println(" ");
//delete first
System.out.println("\nDelete a node at begining and return head: \n");
listnodes first=sl.deletefirst(head);
sl.display(first);
System.out.println(" \n");
//find length
System.out.println("length is="+sl.length(head));
System.out.println(" ");
//Search a node
System.out.println("Search for a node");
if(sl.find(head, 10)){
System.out.println("key found");}
else
System.out.println("key not found");
}

}

Answer 1

    public ListNode insertLast(ListNode head, int data) {
        ListNode newnode = new ListNode(data, null);
        if (head == null) {
            return head;
        }
        ListNode last = head;
        //traverse till the end.
        while (last.link != null) {
            last = last.link;
        }
        //point last node to new node.
        last.link = newnode;
        //return head
        return head;
    }

    public void displayAllNodes(ListNode head) {
        ListNode current = head;
        while (current != null) {
            //print node and point current to next.
            System.out.println(current.data);
            current = current.link;
        }
    }

    //delete at a position(after or before a node)
    public ListNode deleteAtPosition(ListNode head, int position) {
        int currentPosition = 1;
        ListNode current = head;
        ListNode prev = head;
        //move current to node to be deleted.
        while (currentPosition < position) {
            prev = current;
            current = current.link;
            currentPosition++;
        }
        //point previous link to current link. Now prev next is current next, meaning current is deleted.
        prev.link = current.link;
        return head;
    }

Main function :

public static void main(String[] args) {
        System.out.println("Creating a new list with node value 3081");
        ListNode newHead = new ListNode(3081, null);
        SingleLinkList sll = new SingleLinkList();
        System.out.println("Inserting 3 numbers one by one in the end.");
        sll.insertLast(newHead, 3082);
        sll.insertLast(newHead, 3083);
        sll.insertLast(newHead, 3084);
        System.out.println("Displaying all numbers after 3 insertions.");
        sll.displayAllNodes(newHead);
        sll.deleteAtPosition(newHead, 2);
        System.out.println("After deleting node at position 2 :");
        sll.displayAllNodes(newHead);
    }