public static void Main()
Node root2 = new Node(1);
root2.next = new Node(2);
root2.next.next = new Node(3);
root2.next.next.next = new Node(4);
root2.next.next.next.next = new Node(5);
Node r = InvertPairs(root2);
public static void Print(Node n) {
Console.Write(n.data + " -> ");
public static Node InvertPairs(Node head) {
while(head != null && head.next != null) {
if (newHead != null && newHead.next != null) {
head.next = newHead.next;