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.
<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.
<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!