Question

This is a Practice problem for a Exam.

PLEASE WRITE IN JAVA ONLY.

Be able to write the code for inserting a node into a Doubly Linked List.

Please answer the following scenarios

1.At the Start

2.At the End

3.In the Middle

Answer 1

package HomeworkLib;
// Java Program to Implement Doubly Linked List
import java.util.Scanner;
/* creating Class Node for holding data and links to other nodes(previousious and next)*/
class Node
{
protected int data;
protected Node next, previous;

/* default Constructor */
public Node()
{
next = null;
previous = null;
data = 0;
}
/* parameterized Constructor */
public Node(int d, Node n, Node p)
{
data = d;
next = n;
previous = p;
}
/* Function to set data to node */
public void setData(int d)
{
data = d;
}
/* Function to get data of node */
public int getData()
{
return data;
}
}
/* creating Class linkedList */
class linkedList
{
protected Node start;
protected Node end ;
public int size;

/*default Constructor */
public linkedList()
{
start = null;
end = null;
size = 0;
}
/* Function to check if list is empty */
public boolean isEmpty()
{
return start == null;
}
/* Function to get size of list */
public int getSize()
{
return size;
}
/* Function to insert element at begining */
public void insertAtStart(int val)
{
Node newPointer = new Node(val, null, null);
if(start == null)
{
start = newPointer;
end = start;
}
else
{
start.previous=newPointer;
newPointer.next=start;
start = newPointer;
}
//incrementing size of linked list
size++;
}
/* Function to insert element at end */
public void insertAtEnd(int val)
{
Node newPointer = new Node(val, null, null);
if(start == null)
{
start = newPointer;
end = start;
}
else
{
newPointer.previous=end;
end.next=newPointer;
end = newPointer;
}
//incrementing size of linked list
size++;
}
public void insertAtMiddle(int val) {
   Node newPointer = new Node(val, null, null);
   Node myptr=start;
   System.out.print("size: "+size);
   int cnt=(size%2==0)?(size/2 - 1):(((size+1)/2 )-1);
   for(int i=0;i<cnt;i++) {
       myptr=myptr.next;
       System.out.print("data : "+myptr.data);
   }
   newPointer.previous=myptr;
   newPointer.next=myptr.next;
   myptr.next.previous=newPointer;
   myptr.next=newPointer;
   //incrementing size of linked list
   size++;
}
public void display()
{
System.out.print("Doubly Linked List = ");
if (size == 0)
{
System.out.print("empty");
return;
}
if (start.next== null)
{
System.out.println(start.getData() );
return;
}
Node ptr = start;
System.out.print(start.getData()+ " <-> ");
ptr = start.next;
while (ptr.next!= null)
{
System.out.print(ptr.getData()+ " <-> ");
ptr = ptr.next;
}
System.out.print(ptr.getData()+ "\n");
}
}

/*creating Class DoublyLinkedList which involves driver for whole code*/
public class DoublyLinkedList
{
  
public static void main(String[] args)
{
Scanner scan = new Scanner(System.in);
/* Creating object of linkedList */
linkedList list = new linkedList();
System.out.println("Doubly Linked List Test");
char ch;
/* Perform list operations */
do
{
System.out.println("Doubly Linked List Operations");
System.out.println("1. insert at begining");
System.out.println("2. insert at end");
System.out.println("3. insert at middle");
  
System.out.print("Enter your choice: ");
  
//scanning input as string and then converting it to int or we can simply use int choice=scan.nextInt();
String input=scan.next();
int choice =Integer.parseInt(input);
switch (choice)
{
case 1 :
System.out.print("Enter integer element to insert: ");
list.insertAtStart( scan.nextInt() );   
break;
case 2 :
System.out.print("Enter integer element to insert: ");
list.insertAtEnd( scan.nextInt() );   
break;   
case 3 :
System.out.print("Enter integer element to insert: ");
list.insertAtMiddle( scan.nextInt() );   
break;
  
default :
System.out.println("Wrong Entry \n ");
break;   
}
/* Display List */
list.display();
System.out.print("Do you want to continue (Type y or n) : ");
ch = scan.next().charAt(0);

} while (ch == 'Y'|| ch == 'y');
scan.close();
}
}