Java Program For Swapping Nodes In A Linked List Without Swapping Data

// Java program to swap two given nodes 
// of a linked list
class Node 
{
    int data;
    Node next;
    Node(int d)
    {
        data = d;
        next = null;
    }
}

class LinkedList 
{
    // head of list
    Node head; 

    /* Function to swap Nodes x and y in 
       linked list by changing links */
    public void swapNodes(int x, int y)
    {
        // Nothing to do if x and y 
        // are same
        if (x == y)
            return;

        // Search for x (keep track of 
        // prevX and CurrX)
        Node prevX = null, currX = head;
        while (currX != null && 
               currX.data != x) 
        {
            prevX = currX;
            currX = currX.next;
        }

        // Search for y (keep track of 
        // prevY and currY)
        Node prevY = null, currY = head;
        while (currY != null && 
               currY.data != y) 
        {
            prevY = currY;
            currY = currY.next;
        }

        // If either x or y is not present, 
        // nothing to do
        if (currX == null || currY == null)
            return;

        // If x is not head of linked list
        if (prevX != null)
            prevX.next = currY;
        else // make y the new head
            head = currY;

        // If y is not head of linked list
        if (prevY != null)
            prevY.next = currX;
        else // make x the new head
            head = currX;

        // Swap next pointers
        Node temp = currX.next;
        currX.next = currY.next;
        currY.next = temp;
    }

    // Function to add Node at 
    // beginning of list.
    public void push(int new_data)
    {
        // 1. alloc the Node and put the data 
        Node new_Node = new Node(new_data);

        // 2. Make next of new Node as head 
        new_Node.next = head;

        // 3. Move the head to point to new Node 
        head = new_Node;
    }

    /* This function prints contents of 
       linked list starting from the given Node */
    public void printList()
    {
        Node tNode = head;
        while (tNode != null) 
        {
            System.out.print(tNode.data + " ");
            tNode = tNode.next;
        }
    }

    // Driver code
    public static void main(String[] args)
    {
        LinkedList llist = new LinkedList();

        /* The constructed linked list is:
           1->2->3->4->5->6->7 */
        llist.push(7);
        llist.push(6);
        llist.push(5);
        llist.push(4);
        llist.push(3);
        llist.push(2);
        llist.push(1);

        System.out.print(
               "Linked list before calling swapNodes() ");
        llist.printList();
        llist.swapNodes(4, 3);
        System.out.print(
               "Linked list after calling swapNodes() ");
        llist.printList();
    }
}
// This code is contributed by Rajat Mishra

// Java program to swap two given nodes 
// of a linked list
public class Solution 
{
    // Represent a node of the 
    // singly linked list
    class Node 
    {
        int data;
        Node next;

        public Node(int data)
        {
            this.data = data;
            this.next = null;
        }
    }

    // Represent the head and tail
    // of the singly linked list
    public Node head = null;
    public Node tail = null;

    // addNode() will add a new node 
    // to the list
    public void addNode(int data)
    {
        // Create a new node
        Node newNode = new Node(data);

        // Checks if the list is empty
        if (head == null) 
        {
            // If list is empty, both head and
            // tail will point to new node
            head = newNode;
            tail = newNode;
        }
        else 
        {
            // newNode will be added after tail 
            // such that tail's next will point 
            // to newNode
            tail.next = newNode;
            // newNode will become new tail of 
            // the list
            tail = newNode;
        }
    }

    // swap() will swap the given two nodes
    public void swap(int n1, int n2)
    {
        Node prevNode1 = null, prevNode2 = null,
             node1 = head, node2 = head;

        // Checks if list is empty
        if (head == null) 
        {
            return;
        }

        // If n1 and n2 are equal, then
        // list will remain the same
        if (n1 == n2)
            return;

        // Search for node1
        while (node1 != null && 
               node1.data != n1) 
        {
            prevNode1 = node1;
            node1 = node1.next;
        }

        // Search for node2
        while (node2 != null && 
               node2.data != n2) 
        {
            prevNode2 = node2;
            node2 = node2.next;
        }

        if (node1 != null && 
            node2 != null) 
        {
            // If previous node to node1 is not
            // null then, it will point to node2
            if (prevNode1 != null)
                prevNode1.next = node2;
            else
                head = node2;

            // If previous node to node2 is not 
            // null then, it will point to node1
            if (prevNode2 != null)
                prevNode2.next = node1;
            else
                head = node1;

            // Swaps the next nodes of node1 
            // and node2
            Node temp = node1.next;
            node1.next = node2.next;
            node2.next = temp;
        }
        else 
        {
            System.out.println("Swapping is not possible");
        }
    }

    // display() will display all the
    // nodes present in the list
    public void display()
    {
        // Node current will point to head
        Node current = head;

        if (head == null) 
        {
            System.out.println("List is empty");
            return;
        }
        while (current != null) 
        {
            // Prints each node by incrementing 
            // pointer
            System.out.print(current.data + " ");
            current = current.next;
        }
        System.out.println();
    }

    public static void main(String[] args)
    {
        Solution sList = new Solution();

        // Add nodes to the list
        sList.addNode(1);
        sList.addNode(2);
        sList.addNode(3);
        sList.addNode(4);
        sList.addNode(5);
        sList.addNode(6);
        sList.addNode(7);

        System.out.println("Original list: ");
        sList.display();

        // Swaps the node 2 with node 5
        sList.swap(6, 1);

        System.out.println(
               "List after swapping nodes: ");
        sList.display();
    }
}