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Java Program For Finding Length Of A Linked List

  • Last Updated : 27 Dec, 2021

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.

Java




// Java program to count number of 
// nodes in a linked list
  
// Linked list Node
class Node
{
    int data;
    Node next;
    Node(int d)  { data = d;  next = null; }
}
  
// Linked List class
class LinkedList
{
    // Head of list
    Node head;  
  
    // Inserts a new Node at front 
    // of the list.
    public void push(int new_data)
    {
        /* 1 & 2: Allocate the Node &
                  Put in the data*/
        Node 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
    public int getCount()
    {
        Node temp = head;
        int count = 0;
        while (temp != null)
        {
            count++;
            temp = temp.next;
        }
        return count;
    }
  
    // Driver code
    public static void main(String[] args)
    {
        // Start with the empty list 
        LinkedList llist = new LinkedList();
        llist.push(1);
        llist.push(3);
        llist.push(1);
        llist.push(2);
        llist.push(1);
  
        System.out.println("Count of nodes is " +
                            llist.getCount());
    }
}

Output: 

count of nodes is 5

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. 

Java




// Recursive Java program to count number 
// of nodes in a linked list
  
// Linked list Node
class Node
{
    int data;
    Node next;
    Node(int d)  
    {  
        data = d;  
        next = null
    }
}
  
// Linked List class
class LinkedList
{
      
    Node head;  
  
    // Inserts a new Node at front of
    // the list. 
    public void push(int new_data)
    {
        /* 1 & 2: Allocate the Node &
                  Put in the data*/
        Node 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
    public int getCountRec(Node 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() 
    public int getCount()
    {
        return getCountRec(head);
    }
  
    // Driver code
    public static void main(String[] args)
    {
        // Start with the empty list
        LinkedList llist = new LinkedList();
        llist.push(1);
        llist.push(3);
        llist.push(1);
        llist.push(2);
        llist.push(1);
  
        System.out.println("Count of nodes is " +
                            llist.getCount());
    }
}

Output: 

Count of nodes is 5

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


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