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

// JavaScript program to swap two 
// given nodes of a linked list
class Node {
    constructor(val) {
        this.data = val;
        this.next = null;
    }
}

// Head of list
let head;

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

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

    // Search for y (keep track of 
    // prevY and currY)
    let 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
    let temp = currX.next;
    currX.next = currY.next;
    currY.next = temp;
}

// Function to add Node at beginning 
// of list
function push(new_data) {
    // 1. alloc the Node and put the data
    let 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
function printList() {
    let tNode = head;
    while (tNode != null) {
        console.log(tNode.data);
        tNode = tNode.next;
    }
}

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

console.log("Linked list before calling swapNodes()");
printList();
swapNodes(4, 3);
console.log("Linked list after calling swapNodes()");
printList();
// This code is contributed by todaysgaurav

// Javascript program to swap two given 
// nodes of a linked list
// Represent a node of the singly 
// linked list
class Node {
    constructor(val) {
        this.data = val;
        this.next = null;
    }
}

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

// addNode() will add a new node 
// to the list
function addNode(data) {
    // Create a new node
    let 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
function swap(n1, n2) {
    let 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
        let temp = node1.next;
        node1.next = node2.next;
        node2.next = temp;
    }
    else {
        console.log("Swapping is not possible");
    }
}

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

    if (head == null) {
        console.log("List is empty");
        return;
    }
    while (current != null) {
        // Prints each node by incrementing 
        // pointer
        console.log(current.data);
        current = current.next;
    }
}

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

console.log("Original list:");
display();

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

console.log("List after swapping nodes:");
display();
// This code contributed by aashish1995