Pairwise swap of a given linked list by changing links


Input:  1->->2->3->4->5

 Output: 2->1->4->3->5
Code:

 package linkedlist;

 public class Swaplinks {

     Node head = null;

     void swap(){
      
        Node prev = head;
        Node curr = head.next;
        head = curr;
      

        while(true){
          
            Node temp = curr.next;
            curr.next = prev;
          
            //for last node or null node
            if(temp == null || temp.next == null){
                prev.next = temp;
                break;
            }
          
            //prev.next is pointing to temp.next considering next swap
            prev.next = temp.next;
          
            prev = temp;
            curr = prev.next;

         }
      

        return;
    }

     void printlist() {

         Node temp = head;

         while (temp != null) {
            System.out.print(temp.data + " ");
            temp = temp.next;
        }
        System.out.println("");
    }

     public static void main(String[] args){

         Swaplinks list = new Swaplinks();

         list.head = new Node(1);
        list.head.next = new Node(2);
        list.head.next.next = new Node(3);
        list.head.next.next.next = new Node(4);
        list.head.next.next.next.next = new Node(5);

         list.printlist();

         list.swap();

         list.printlist();
    }

 }
Illustraion:








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