PairWiseSwap.cpp

// C++ program to pairwise swap elements
// in a given linked list
#include <bits/stdc++.h>
using namespace std;
 
/* A linked list node */
class Node {
public:
    int data;
    Node* next;
};
 
/* Function to pairwise swap elements
of a linked list */
void pairWiseSwap(Node* head)
{
    Node* temp = head;
 
    /* Traverse further only if
    there are at-least two nodes left */
    while (temp != NULL && temp->next != NULL) {
        /* Swap data of node with
           its next node's data */
        swap(temp->data,
             temp->next->data);
 
        /* Move temp by 2 for the next pair */
        temp = temp->next->next;
    }
}
 
/* Function to add a node at the
   beginning of Linked List */
void push(Node** head_ref, int new_data)
{
    /* allocate node */
    Node* new_node = new Node();
 
    /* put in the data */
    new_node->data = new_data;
 
    /* link the old list off the new node */
    new_node->next = (*head_ref);
 
    /* move the head to point
       to the new node */
    (*head_ref) = new_node;
}
 
/* Function to print nodes
   in a given linked list */
void printList(Node* node)
{
    while (node != NULL) {
        cout << node->data << " ";
        node = node->next;
    }
}
 
// Driver Code
int main()
{
    Node* start = NULL;
 
    /* The constructed linked list is:
    1->2->3->4->5 */
    push(&start, 5);
    push(&start, 4);
    push(&start, 3);
    push(&start, 2);
    push(&start, 1);
 
    cout << "Linked list "
         << "before calling pairWiseSwap()\n";
    printList(start);
 
    pairWiseSwap(start);
 
    cout << "\nLinked list "
         << "after calling pairWiseSwap()\n";
    printList(start);
 
    return 0;
}