Pairwise swap elements of a linked list

Given a singly linked list of size N. The task is to swap elements in the linked list pairwise.

For example, if the input list is 1 2 3 4, the resulting list after swaps will be 2 1 4 3.

Note: You need to swap the nodes, not only the data. If only data is swapped then driver will print -1.

Example 1:

Input:

LinkedList: 1->2->2->4->5->6->7->8

Output: 2 1 4 2 6 5 8 7

Explanation: After swapping each pair

considering (1,2), (2, 4), (5, 6).. so

on as pairs, we get 2, 1, 4, 2, 6, 5,

8, 7 as a new linked list.

c++ implementation:

Node* pairWiseSwap(Node* head)
{
   Node*temp=head;
   Node*h=NULL;
   int c=0;
   while(temp!=NULL)
   {
      if(temp->next!=NULL)
      cout<< temp->next->data<<" ";
      else
      {
      cout<<temp->data;
      return h;
      }
      cout<<temp->data<<" ";
     if(temp->next->next!=NULL)
      temp=temp->next->next;
      else
      return h;
    }
   return h;
}

Time Complexity: O(n)