Javascript Program For Finding Length Of A Linked List

Last Updated : 10 Sep, 2024

Write a function to count the number of nodes in a given singly linked list.

linkedlist_find_length

For example, the function should return 5 for linked list 1->3->1->2->1.

Iterative Solution:

1) Initialize count as 0 
2) Initialize a node pointer, current = head.
3) Do following while current is not NULL
 a) current = current -> next
 b) count++;
4) Return count

Following is the Iterative implementation of the above algorithm to find the count of nodes in a given singly linked list.

JavaScript

// Javascript program to count number  // of nodes in a linked list // Linked list Node class Node {  constructor(val) {  this.data = val;  this.next = null;  } } // Head of list let head; // Inserts a new Node at front of the list. function push(new_data) {  // 1 & 2: Allocate the Node & Put in   // the data  let new_node = new Node(new_data);  // 3. Make next of new Node as head  new_node.next = head;  // 4. Move the head to point to new Node  head = new_node; } // Returns count of nodes in linked list  function getCount() {  let temp = head;  let count = 0;  while (temp != null) {  count++;  temp = temp.next;  }  return count; } // Driver code // Start with the empty list push(1); push(3); push(1); push(2); push(1); console.log("Count of nodes is " + getCount()); // This code contributed by Rajput-Ji

Output

Count of nodes is 5

Complexity Analysis:

Time Complexity: O(n), where n represents the length of the given linked list.
Auxiliary Space: O(1), no extra space is required, so it is a constant.

Recursive Solution:

int getCount(head)
1) If head is NULL, return 0.
2) Else return 1 + getCount(head->next)

Following is the Recursive implementation of the above algorithm to find the count of nodes in a given singly linked list.

JavaScript

// Recursive javascript program to count // number of nodes in a linked list // Linked list Node class Node {  constructor(val) {  this.data = val;  this.next = null;  } } // Linked List class // Head of list let head; // Inserts a new Node at front of the list. function push(new_data) {  // 1 & 2: Allocate the Node &   // Put in the data  let new_node = new Node(new_data);  // 3. Make next of new Node as head  new_node.next = head;  // 4. Move the head to point to new Node  head = new_node; } // Returns count of nodes in linked list function getCountRec(node) {  // Base case  if (node == null)  return 0;  // Count is this node plus rest   // of the list  return 1 + getCountRec(node.next); } // Wrapper over getCountRec() function getCount() {  return getCountRec(head); } // Driver code // Start with the empty list  push(1); push(3); push(1); push(2); push(1); console.log("Count of nodes is " + getCount()); // This code contributed by gauravrajput1

Output

Count of nodes is 5

Complexity Analysis:

Time Complexity: O(n), where n represents the length of the given linked list.
Auxiliary Space: O(n), for recursive stack where n represents the length of the given linked list.

Please refer complete article on Find Length of a Linked List (Iterative and Recursive) for more details!