Javascript Program For Finding Length Of A Linked List

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

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

<script>
// 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
var head; 
 
// Inserts a new Node at front of the list.
function push(new_data) 
{
    // 1 & 2: Allocate the Node & Put in 
    // the data
    var 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() 
{
    var temp = head;
    var 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);
 
document.write("Count of nodes is " + getCount());
 
// This code contributed by Rajput-Ji 
</script>

Output:

count of nodes is 5

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

<script>
// 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
var head; 
 
// Inserts a new Node at front of the list.
function push( new_data) 
{
    // 1 & 2: Allocate the Node & 
    // Put in the data
    var 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);
 
document.write("Count of nodes is " + getCount());
 
// This code contributed by gauravrajput1
</script>

Output:

Count of nodes is 5

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!

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