JavaScript Exercises: Remove the tail element from a Singly Linked list

JavaScript Singly Linked List: Exercise-14 with Solution

Write a JavaScript program that removes the tail element from a Singly Linked list.

Sample Solution:

JavaScript Code:

// Define a class representing a node in a singly linked list
class Node {
    constructor(data) {
        // Initialize the node with provided data
        this.data = data;
        // Initialize the next pointer to null
        this.next = null;
    }
}

// Define a class representing a singly linked list
class SinglyLinkedList {
    constructor(Head = null) {
        // Initialize the head of the list
        this.Head = Head;
    }

    // Method to add a new node to the end of the list
    add(newNode) {
        // Start traversal from the head node
        let node = this.Head;
        // If the list is empty, set the new node as the head and return
        if (node == null) {
            this.Head = newNode;
            return;
        }
        // Traverse the list until the last node
        while (node.next) {
            node = node.next;
        }
        // Set the next pointer of the last node to the new node
        node.next = newNode;
    }

    // Method to remove a node at a specified index position
    removeAt(index_pos) {
        // Start traversal from the head node
        let nodes = this.Head;
        // If index position is 0, remove the head node
        if (index_pos === 0) {
            if (nodes !== null) {
                nodes = nodes.next;
                this.Head = nodes;
            } else {
                throw Error("Index Out of Bound");
            }
            return;
        }
        // Traverse the list until the previous node of the node to be removed
        while (--index_pos) {
            if (nodes.next !== null) {
                nodes = nodes.next;
            } else {
                throw Error("Index Out of Bound");
            }
        }
        // Remove the node by skipping its reference in the list
        nodes.next = nodes.next.next;
    }

    // Method to get the size of the list
    size() {
        let current = this.Head;
        let count = 0;
        // Traverse the list and count the number of nodes
        while (current) {
            count++;
            current = current.next;
        }
        return count;
    }

    // Method to delete the last item from the list
    deleteTail() {
        // Call removeAt method to remove the node at the last index position
        this.removeAt(this.size() - 1);
    }

    // Method to display the elements of the list
    displayList() {
        // Start traversal from the head node
        let node = this.Head;
        // Initialize an empty string to store the elements of the list
        var str = "";
        // Traverse the list and concatenate each element to the string
        while (node) {
            str += node.data + "->";
            node = node.next;
        }
        // Append "NULL" to indicate the end of the list
        str += "NULL";
        // Print the string containing the list elements
        console.log(str);
    }
}

// Create an instance of the SinglyLinkedList class
let numList = new SinglyLinkedList();
// Add nodes with data values to the list
numList.add(new Node(12));
numList.add(new Node(13));
numList.add(new Node(14));
numList.add(new Node(15));
numList.add(new Node(14));
// Display the elements of the list
console.log("Singly Linked list:");
numList.displayList();
// Remove the last element from the list
console.log("Remove the tail from the said Singly Linked list:");
numList.deleteTail();
numList.displayList();
// Again remove the last element from the list
console.log("Again remove the tail from the said Singly Linked list:");
numList.deleteTail();
numList.displayList();

Output:

Singly Linked list:
12->13->14->15->14->NULL
Remove the tail from the said Singly Linked list:
12->13->14->15->NULL
Again remove the tail from the said Singly Linked list:
12->13->14->NULL

Flowchart:

Live Demo:

See the Pen javascript-singly-linked-list-exercise-14 by w3resource (@w3resource) on CodePen.

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