CODE EXAMPLE FOR CPP

Swap given nodes in a Doubly Linked List without modifying data

// C++ code to implement the above approach
 
#include <bits/stdc++.h>
using namespace std;
 
// Link list Node Class
class Node {
public:
    int data;
    Node* prev;
    Node* next;
 
    // Constructor function
    Node(int data)
    {
        this->data = data;
        this->prev = NULL;
        this->next = NULL;
    }
};
 
// Function to print linked list
void print(Node* head)
{
    Node* temp = head;
 
    // Iterate until node is NOT NULL
    while (temp != NULL) {
        cout << temp->data << " ";
        temp = temp->next;
    }
    cout << endl;
}
 
// Function to push a node in DLL
void push(Node*& head, Node*& tail,
          int item)
{
 
    // DLL is empty
    if (tail == NULL) {
 
        Node* temp = new Node(item);
        tail = temp;
        head = temp;
    }
 
    // DLL is not empty
    else {
        Node* temp = new Node(item);
        tail->next = temp;
        temp->prev = tail;
        tail = temp;
    }
}
 
// Function to find the nodes
// which have to be swapped
pair<Node*, Node*> find(Node*& head,
                        int x, int y)
{
    Node* N1 = NULL;
    Node* N2 = NULL;
    Node* temp = head;
 
    // Traversing the list
    while (temp != NULL) {
        if (temp->data == x)
            N1 = temp;
        else if (temp->data == y)
            N2 = temp;
        temp = temp->next;
    }
    return make_pair(N1, N2);
}
 
// Function to swap the nodes
// consisting of x and y
void swap(Node*& head, Node*& tail,
          int x, int y)
{
 
    // Edge Cases
    if (head == NULL || head->next == NULL
        || x == y)
        return;
 
    // Finding the Nodes
    pair<Node*, Node*> p = find(head, x, y);
 
    Node* Node1 = p.first;
    Node* Node2 = p.second;
 
    if (Node1 == head)
        head = Node2;
    else if (Node2 == head)
        head = Node1;
    if (Node1 == tail)
        tail = Node2;
    else if (Node2 == tail)
        tail = Node1;
 
    // Swapping Node1 and Node2
    Node* temp;
    temp = Node1->next;
    Node1->next = Node2->next;
    Node2->next = temp;
 
    if (Node1->next != NULL)
        Node1->next->prev = Node1;
    if (Node2->next != NULL)
        Node2->next->prev = Node2;
 
    temp = Node1->prev;
    Node1->prev = Node2->prev;
    Node2->prev = temp;
 
    if (Node1->prev != NULL)
        Node1->prev->next = Node1;
    if (Node2->prev != NULL)
        Node2->prev->next = Node2;
}
 
// Driver Code
int main()
{
 
    Node* head = NULL;
    Node* tail = NULL;
 
    push(head, tail, 1);
    push(head, tail, 8);
    push(head, tail, 7);
    push(head, tail, 9);
    push(head, tail, 4);
 
    int X = 1, Y = 4;
 
    cout << "Before Swapping: ";
    print(head);
 
    swap(head, tail, X, Y);
    cout << "After Swapping: ";
    print(head);
 
    return 0;
}