Java Program find below the previous code public class LinkList { IntegerNode he

Question

Java Program

find below the previous code

public class LinkList
{
        IntegerNode head;         // Header Delcaration      
       public void insert(int pos, IntegerNode item)    //add one node there
       {
           IntegerNode dummy = new IntegerNode(-1, null); // dummy node will assist in setting the link
           dummy.next = head;  
           IntegerNode curr = dummy;  
           while(--pos >= 0)                            // find the position, curr.next will be right position to add new node there
           {
               curr = curr.next;              
           }  
           item.next = curr.next;                     //insert the node from current to next
           curr.next = item;  
           head = dummy.next;                          // update head
       }
       public IntegerNode get(int pos)               //get int pos
       {
           IntegerNode gets = head;
           if(pos+1 == 0)                          
           {
               return gets;
           }
           for(int i=0;i<pos+1;i++) //updating the link by 1
               {
                   gets = gets.next;
               }
               return gets;
       }
       public void remove(int value)
       {
           IntegerNode l1 = head;                   //create two other references that will used as instruction
           IntegerNode l2 = head.next;  
               while(l2!=null)                           //check if the l2 is equal to value until the l2 reaches end
               {
                   if(l2.item==value)
                   {
                       l1.next = l2.next;
                       l2.next = null;
                   }
                   l2 = l2.next;                       //updating references by one element
                   l1 = l1.next;
               }
       }
       public String toString()   //return the string representation of the list
       {
           StringBuilder ret = new StringBuilder();
           IntegerNode curr = head;  
           while (curr != null)
           {
               if(curr != head)
               {
                   ret.append("->");
               }
               ret.append(curr.item);
               curr = curr.next;
           }          
           return ret.toString();          
       }      
       public static void main(String[] args)
             {
               LinkList list = new LinkList();
               list.insert(0,new IntegerNode(10));
              list.insert(0,new IntegerNode(20));
              IntegerNode s = list.get(1);
              System.out.println("Item at index 1 is " + s );
              list.insert(2,new IntegerNode(30));      
              System.out.println("Before removing: ");
               System.out.println(list);
               list.remove(10);
              System.out.println("After removing: ");
              System.out.println(list);
       }   
}

E xer se 4: CheckPalindrome: You have implemented LinkList Class for yor Prog#4 Exercise#4, which should have insert and remove methods implemented. Now you need to implement one more method checkPalindromeO, which is to check if the LinkList is a palindrome or not. Return true if the linklist is palindrome; otherwise, return false Example: 1-> 2--> 3 -> 2-> 1 => true false Please use the following program to test your code. public static void main( String [l args) f LinkList list = new LinkList(); list insert (0, new IntegerNode (1O)) list insert (0, new IntegerNode (20)) list.insert (0, new IntegerNode (10)); System.out println(list) System.out pxintin (list. checkPalindrome ()) list.insert.(l,new IntegerNode (30)) System.out.pxintln(list) System.out println (list. checkPalindrome 0)

Explanation / Answer

Brief description of the algorithm: I used a stack. First I will traverse from left to right in the linked list and push item in that node into the stack. Then I traverse Linkedlist for the second time this time I will check top of the stack with the item in the curr node if it matches I move on or it is not a palindrome. If I reach the end with out a mismatch then it's a palindrome.

public bool checkPalindrome(){
    Stack st = new Stack();
    IntegerNode curr = head;
while (curr != null)
{
    st.push(new Integer(curr.item));
curr = curr.next;
}
curr=head;
while(curr!=null)
{
    if(st.peek()!=new Integer(curr).item){
        return false;
    }
}
return true;
}

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