Question

public class IntNode      
        {
           private int data;
           private IntNode link;
           public IntNode(int data, IntNode link){.. }
           public int     getData( )          {.. }
           public IntNode getLink( )           {.. }
           public void    setData(int data)     {.. }
           public void    setLink(IntNode link) {.. }
        }

All questions are based on the above class, and the following declaration.  

// Declare an empty, singly linked list with a head and a tail reference.

// you need to make sure that head always points to the head node and tail always points to the tail node.
         IntNode head, tail;
         head = tail = null;    

// 1.) Insert a node with data 2 into this empty list

// 2.) Insert a node with data 4 at the end of the list.

// 3.) Insert a node with data 3 between the first and the last node.

// 4.) Insert a node with data 1 before the first node.

// 5.) delete the node with data 2

// 6.) delete the node with data 1

Answer 1

Program

public class IntNode
{
   private int data;
    private IntNode link;
public IntNode(int data, IntNode link){
   this.data = data;
   this.link = link;
}
public int getData(){
   return data;
}
public IntNode getLink(){
   return link;
}
public void setData(int data){
   this.data = data;
}
public void setLink(IntNode link){
   this.link = link;
}
}

class SLinkedList{
   private IntNode head;
   private IntNode tail;
  
   //constructor
   public SLinkedList(){
       head = null;
       tail = null;
   }
  
   //method to insert an item to beginning of the list
   public void insertAtBegin(int item)
   {
       IntNode newnode = new IntNode(item, head);
       if(head==null)
       {
           head = tail = newnode;
       }
       else
       {
           head = newnode;
       }
   }
  
   //method to insert an item to end of the list
   public void insertAtEnd(int item)
   {
       IntNode newnode = new IntNode(item, null);
       if(tail==null)
       {
           head = tail = newnode;
       }
       else
       {
           tail.setLink(newnode);
           tail = newnode;
       }
   }
  
   //method to insert an item to the list
   public void insert(int item)
   {
       IntNode newnode = new IntNode(item, null);
      
       if(head==null)
       {
           head = tail = newnode;
       }
       else
       {
           IntNode temp = head;
           IntNode pre = null;
          
           while(temp!= null && temp.getData()<item)
           {
               pre = temp;
               temp = temp.getLink();
           }
          
           pre.setLink(newnode);
           newnode.setLink(temp);
       }
   }
  
   //method to delete an item from the list
   public void delete(int item)
   {
       if(head==null){
           System.out.println ("List is empty");
           return;
       }
  
       IntNode temp = head;
       IntNode prev = null;
      
       if(temp.getData()==item)
       {
           head = temp.getLink();
           System.out.println (item + " has been deleted");
           return;
       }
      
       while(temp!= null && temp.getData()!=item)
       {
           prev = temp;
           temp = temp.getLink();
       }
      
       if(temp==null)
       {
           System.out.println (item + " was not found");
           return;
       }
      
       prev.setLink(temp.getLink());
       System.out.println (item + " has been deleted");
   }
  
   //method to print the list
   public void printList()
   {
       if(head==null)
       {
           System.out.println ("List is empty");
           return;
       }
      
       System.out.print("List: ");
       IntNode temp = head;
      
       while(temp!= null)
       {
           System.out.print (temp.getData() + " ");
           temp = temp.getLink();
       }
       System.out.println ();
   }
}

class LinkedListDemo
{
   //main method
   public static void main (String[] args)
   {
       //create object of SLinkedList
       SLinkedList list = new SLinkedList();
      
       // 1.) Insert a node with data 2 into this empty list
       list.insert(2);
       System.out.println ("After insert 2: ");
       list.printList();
       // 2.) Insert a node with data 4 at the end of the list.
       list.insertAtEnd(4);
       System.out.println ("After insert 4: ");
       list.printList();
       // 3.) Insert a node with data 3 between the first and the last node.
       list.insert(3);
       System.out.println ("After insert 3: ");
       list.printList();
       // 4.) Insert a node with data 1 before the first node.
       list.insertAtBegin(1);
       System.out.println ("After insert 1: ");
       list.printList();
       // 5.) delete the node with data 2
       list.delete(2);
       System.out.println ("After delete 2: ");
       list.printList();
       // 6.) delete the node with data 1
       list.delete(1);
       System.out.println ("After delete 1: ");
       list.printList();
   }
}

Output:

After insert 2:
List: 2
After insert 4:
List: 2 4
After insert 3:
List: 2 3 4
After insert 1:
List: 1 2 3 4
2 has been deleted
After delete 2:
List: 1 3 4
1 has been deleted
After delete 1:
List: 3 4

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