/**
 * Definition for singly-linked list.
 * public class ListNode {
 *     int val;
 *     ListNode next;
 *     ListNode(int x) { val = x; }
 * }
 */
class Solution {
 public ListNode swapPairs(ListNode head) {
	        if(head==null)
                return null;
	    	ListNode next=null;
	    	ListNode current = head;
	    	ListNode newHead = null;
	    	ListNode prev=null;
	    	next = current.next;
	    	if(next!=null) {
	    		newHead = next;
	    	}
	        while(current!=null && next!=null) {
	        	current.next = next.next;
	        	next.next = current;
	            //print(newHead);
	        	prev = current;
	        	current = current.next;
                if(current!=null)
	        	    next = current.next;
	        	if(prev!=null && current!=null && next!=null) {
	        		prev.next = next;
	        	}else if(prev!=null && current!=null && next==null){
                    prev.next=current;
                }


	        }
	        if(newHead !=null)
	        	return newHead;
	        return head;

	    }

//     void print(ListNode node){

// 		ListNode newNode = node;
// 		while(newNode!=null) {
// 			System.out.print(newNode.val+" -> ");
//             newNode = newNode.next;
// 		}
// 		System.out.println();
//     }



}