Swap nodes in pairs : 2 methods

 Method1: iterative approach

Start traversing from the head, swap data of each node with the data of its next node. 

class node{}

void pairwiseswap(node* head) 

{

   node *temp= head; 

//traverse only if atlest 2 nodes are left

while(temp!=NULL && temp->next!=NULL)

{

  swap(temp->data, temp->next->data);

temp->next->next; //move temp by 2 units for next pair wise swap

}  //while loopends

}  //function ends

void push(node** head_ref, int new_data) {}

void printlist(node *head) {}

int main() {}

Recursive approach: by using a function

void pairwiseswap(struct node * head)

{

   if (head!=NULL  && head->next!=NULL) //if there are atleast 2 nodes

 {

      //swap head and head next data 

     swap(head->data, head->next->data);  

      

       //call pairwiseswap method/fuction for rest              of  list

      pairwiseswap(head->next->next)

 } //if ends

} //function