JavaScript Exercises: Remove a node at the specified index in a Doubly linked lists
JavaScript Data Structures: Exercise-14 with Solution
Remove the node from a DLL at the specified index
Write a JavaScript program that removes the node from the Doubly linked lists at the specified index.
Sample Solution:
JavaScript Code:
class Node {
// Constructor function for creating a new node with a given value
constructor(value) {
this.value = value; // Assign the given value to the node
this.next = null; // Initialize the pointer to the next node as null
this.previous = null; // Initialize the pointer to the previous node as null
}
}
class DoublyLinkedList {
// Constructor function for creating a new doubly linked list with a head node having the given value
constructor(value) {
// Initialize the head node with the given value and no next or previous node
this.head = {
value: value, // Store the value of the head node
next: null, // Pointer to the next node in the list, initially set to null
previous: null // Pointer to the previous node in the list, initially set to null
};
this.length = 0; // Initialize the length of the list to 0
this.tail = this.head; // Set the tail node to the head node initially
}
add(newNode) {
if (this.head === null) {
this.head = newNode; // If the list is empty, set the new node as the head
this.tail = newNode; // Also set the new node as the tail
}
else
{
newNode.previous = this.tail; // Set the previous pointer of the new node to the current tail node
this.tail.next = newNode; // Set the next pointer of the current tail node to the new node
this.tail = newNode; // Update the tail node to the new node
}
this.length++; // Increment the length of the list
}
delete(index) {
if (index < 0 || index >= this.length) return null; // Check if the index is valid
if (index === 0) return this.shift(); // If index is 0, remove the first node
if (index === this.length - 1) return this.pop(); // If index is the last one, remove the last node
let current = this.head; // Start from the head of the list
let ctr = 0; // Counter to track the index
while (ctr !== index) { // Iterate until reaching the node to be removed
current = current.next; // Move to the next node
ctr++; // Increment the counter
}
current.previous.next = current.next; // Adjust the next pointer of the previous node
current.next.previous = current.previous; // Adjust the previous pointer of the next node
this.length--; // Decrement the length of the list
return current; // Return the removed node
}
shift() {
if (!this.head) return null; // Check if the list is empty
let old_Head = this.head; // Store the reference to the current head node
if (this.length === 1) { // Check if there is only one node in the list
this.head = null; // If yes, set head to null
this.tail = null; // Also set tail to null
} else { // If there are more than one node in the list
this.head = old_Head.next; // Update the head to the next node
this.head.previous = null; // Set the previous pointer of the new head to null
old_Head.next = null; // Set the next pointer of the old head to null
}
this.length--; // Decrement the length of the list
return old_Head; // Return the removed node (old head)
}
pop() {
if (!this.tail) return null; // Check if the list is empty
let pNode = this.tail; // Store the reference to the current tail node
if (this.length === 1) { // Check if there is only one node in the list
this.head = null; // If yes, set head to null
this.tail = null; // Also set tail to null
} else { // If there are more than one node in the list
this.tail = pNode.previous; // Update the tail to the previous node
this.tail.next = null; // Set the next pointer of the new tail to null
pNode.previous = null; // Set the previous pointer of the old tail to null
}
this.length--; // Decrement the length of the list
return pNode; // Return the removed node (old tail)
}
printList(){
let current = this.head; // Start from the head of the list
let result = []; // Array to store the values of the nodes
while (current !== null) { // Iterate through the list until reaching the end
result.push(current.value); // Push the value of the current node to the array
current = current.next; // Move to the next node
}
console.log(result.join(' ')); // Log the values of the nodes separated by space
return this; // Return the DoublyLinkedList object for chaining
}
}
let numList = new DoublyLinkedList(); // Create a new instance of the DoublyLinkedList class
numList.add(new Node(2)); // Add nodes to the list
numList.add(new Node(3));
numList.add(new Node(4));
numList.add(new Node(5));
numList.add(new Node(6));
numList.add(new Node(7));
console.log("Original Doubly Linked Lists:"); // Print the original list
numList.printList();
console.log("Remove the node,index = 5");
numList.delete(5)
numList.printList();
console.log("Remove the node,index = 4");
numList.delete(4)
numList.printList();
console.log("Remove the node,index = 2");
numList.delete(2)
numList.printList();
Output:
Original Doubly Linked Lists: 2 3 4 5 6 7 Remove the node,index = 5 2 3 4 5 6 Remove the node,index = 4 2 3 4 5 Remove the node,index = 2 2 4 5
Flowchart:
Live Demo:
See the Pen javascript-doubly-linked-list-exercise-14 by w3resource (@w3resource) on CodePen.
For more Practice: Solve these Related Problems:
- Write a JavaScript function that removes the node at a specified index in a doubly linked list and updates the surrounding pointers.
- Write a JavaScript function that iterates through a DLL to remove a node at the given position and returns the modified list.
- Write a JavaScript function that validates the removal index and handles errors if the index is out of range.
- Write a JavaScript function that removes a node from a DLL using recursion and returns the updated list structure.
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