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.
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
Java Programming:
// 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; // head of list
/* 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;
}
/* 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)
{
/* 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());
}
}
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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)
Java Programming:
// 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; // head of list
/* 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);
}
/* 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)
{
/* 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());
}
}
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Output:
count of nodes is 5