# Find Length of a Linked List (Iterative and Recursive)

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

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

## Recommended: Please solve it on “PRACTICE” first, before moving on to the solution.

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 are C/C++, Java and Python implementations of above algorithm to find count of nodes.

## C/C++

```// Iterative C program to find length or count of nodes in a linked list
#include<stdio.h>
#include<stdlib.h>

struct Node
{
int data;
struct Node* next;
};

/* Given a reference (pointer to pointer) to the head
of a list and an int, push a new node on the front
of the list. */
void push(struct Node** head_ref, int new_data)
{
/* allocate node */
struct Node* new_node =
(struct Node*) malloc(sizeof(struct Node));

/* put in the data  */
new_node->data  = new_data;

/* link the old list off the new node */

/* move the head to point to the new node */
}

/* Counts no. of nodes in linked list */
{
int count = 0;  // Initialize count
struct Node* current = head;  // Initialize current
while (current != NULL)
{
count++;
current = current->next;
}
return count;
}

/* Drier program to test count function*/
int main()
{

/* Use push() to construct below list
1->2->1->3->1  */

/* Check the count function */
printf("count of nodes is %d", getCount(head));
return 0;
}
```

## Java

```// Java program to count number of nodes in a linked list

class Node
{
int data;
Node next;
Node(int d)  { data = d;  next = null; }
}

{

/* 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 */

/* 4. Move the head to point to new Node */
}

/* Returns count of nodes in linked list */
public int getCount()
{
int count = 0;
while (temp != null)
{
count++;
temp = temp.next;
}
return count;
}

/* Drier program to test above functions. Ideally
this function should be in a separate user class.
It is kept here to keep code compact */
public static void main(String[] args)
{
llist.push(1);
llist.push(3);
llist.push(1);
llist.push(2);
llist.push(1);

System.out.println("Count of nodes is " +
llist.getCount());
}
}
```

## Python

```# A complete working Python program to find length of a

# Node class
class Node:
# Function to initialise the node object
def __init__(self, data):
self.data = data # Assign data
self.next = None # Initialize next as null

# Linked List class contains a Node object

def __init__(self):

# This function is in LinkedList class. It inserts
# a new node at the beginning of Linked List.
def push(self, new_data):

# 1 & 2: Allocate the Node &
#     Put in the data
new_node = Node(new_data)

# 3. Make next of new Node as head

# 4. Move the head to point to new Node

# This function counts number of nodes in Linked List
# iteratively, given 'node' as starting node.
def getCount(self):
temp = self.head # Initialise temp
count = 0 # Initialise count

# Loop while end of linked list is not reached
while (temp):
count += 1
temp = temp.next
return count

# Code execution starts here
if __name__=='__main__':
llist.push(1)
llist.push(3)
llist.push(1)
llist.push(2)
llist.push(1)
print ("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 are C/C++, Java and Python implementations of above algorithm to find count of nodes.

## C/C++

```// Recursive C program to find length or count of nodes in a linked list
#include<stdio.h>
#include<stdlib.h>

struct Node
{
int data;
struct Node* next;
};

/* Given a reference (pointer to pointer) to the head
of a list and an int, push a new node on the front
of the list. */
void push(struct Node** head_ref, int new_data)
{
/* allocate node */
struct Node* new_node =
(struct Node*) malloc(sizeof(struct Node));

/* put in the data  */
new_node->data  = new_data;

/* link the old list off the new node */

/* move the head to point to the new node */
}

/* Counts the no. of occurences of a node
{
// Base case
return 0;

// count is 1 + count of remaining list
}

/* Drier program to test count function*/
int main()
{

/* Use push() to construct below list
1->2->1->3->1  */

/* Check the count function */
printf("count of nodes is %d", getCount(head));
return 0;
}
```

## Java

```// Recursive Java program to count number of nodes in

class Node
{
int data;
Node next;
Node(int d)  { data = d;  next = null; }
}

{

/* 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 */

/* 4. Move the head to point to 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()
{
}

/* Drier program to test above functions. Ideally
this function should be in a separate user class.
It is kept here to keep code compact */
public static void main(String[] args)
{
llist.push(1);
llist.push(3);
llist.push(1);
llist.push(2);
llist.push(1);

System.out.println("Count of nodes is " +
llist.getCount());
}
}
```

## Python

```# A complete working Python program to find length of a

# Node class
class Node:
# Function to initialise the node object
def __init__(self, data):
self.data = data  # Assign data
self.next = None  # Initialize next as null

# Linked List class contains a Node object

def __init__(self):

# This function is in LinkedList class. It inserts
# a new node at the beginning of Linked List.
def push(self, new_data):

# 1 & 2: Allocate the Node &
#        Put in the data
new_node = Node(new_data)

# 3. Make next of new Node as head

# 4. Move the head to point to new Node

# This function counts number of nodes in Linked List
# recursively, given 'node' as starting node.
def getCountRec(self, node):
if (not node): # Base case
return 0
else:
return 1 + self.getCountRec(node.next)

# A wrapper over getCountRec()
def getCount(self):

# Code execution starts here
if __name__=='__main__':
llist.push(1)
llist.push(3)
llist.push(1)
llist.push(2)
llist.push(1)
print 'Count of nodes is :',llist.getCount()
```

Output:
`count of nodes is 5`

# GATE CS Corner    Company Wise Coding Practice

Please write to us at contribute@geeksforgeeks.org to report any issue with the above content.
1.4 Average Difficulty : 1.4/5.0
Based on 100 vote(s)