Javascript Program For Deleting A Given Node In Linked List Under Given Constraints

Last Updated : 05 Sep, 2024

Given a Singly Linked List, write a function to delete a given node. Your function must follow following constraints:

It must accept a pointer to the start node as the first parameter and node to be deleted as the second parameter i.e., a pointer to head node is not global.
It should not return a pointer to the head node.
It should not accept pointer to pointer to the head node.

You may assume that the Linked List never becomes empty.
Let the function name be deleteNode(). In a straightforward implementation, the function needs to modify the head pointer when the node to be deleted is the first node. As discussed in previous post, when a function modifies the head pointer, the function must use one of the given approaches, we can't use any of those approaches here.

Solution:

We explicitly handle the case when the node to be deleted is the first node, we copy the data of the next node to head and delete the next node. The cases when a deleted node is not the head node can be handled normally by finding the previous node and changing next of the previous node. The following are the implementation.

JavaScript

// javascript program to delete a given node 
// in linked list under given constraints
let head;

class Node {
    constructor(val) {
        this.data = val;
        this.next = null;
    }
}

function deleteNode(node, n) {

    // When node to be deleted is head node
    if (node == n) {
        if (node.next == null) {
            console.log("There is only one node. The list can't be made empty ");
            return;
        }

        /* Copy the data of next node to head */
        node.data = node.next.data;

        // store address of next node
        n = node.next;

        // Remove the link of next node
        node.next = node.next.next;

        // free memory


        return;
    }

    // When not first node, follow the normal deletion process
    // find the previous node
    prev = node;
    while (prev.next != null && prev.next != n) {
        prev = prev.next;
    }

    // Check if node really exists in Linked List
    if (prev.next == null) {
        console.log("Given node is not present in Linked List");
        return;
    }

    // Remove node from Linked List
    prev.next = prev.next.next;
    return;
}

/* Utility function to print a linked list */
function printList(head) {
    while (head != null) {
        console.log(head.data + " ");
        head = head.next;
    }
    console.log("");
}

head = new Node(12);
head.next = new Node(15);
head.next.next = new Node(10);
head.next.next.next = new Node(11);
head.next.next.next.next = new Node(5);
head.next.next.next.next.next = new Node(6);
head.next.next.next.next.next.next = new Node(2);
head.next.next.next.next.next.next.next = new Node(3);

console.log("Given Linked List :");
printList(head);

// Let us delete the node with value 10
console.log("Deleting node :" + head.next.next.data);
deleteNode(head, head.next.next);

console.log("Modified Linked list :");
printList(head);

// Lets delete the first node
console.log("Deleting first Node.");
deleteNode(head, head);
console.log("Modified Linked List:");
printList(head);

// This code is contributed by todaysgaurav

Output

Given Linked List :
12 
15 
10 
11 
5 
6 
2 
3 

Deleting node :10
Modified Linked list :
12 
15 
11 
5 
6 
2 
3 

Deleting first Node.
Modified Linked List:
15 
11 
5 
6 
2 
3