How to insert a new node after a given node in a linked list?

Article by: Manish Methani

Last Updated: October 3, 2021 at 10:04am IST
3 min 23 sec

Linked List insertion can be done using three ways,

1) Insertion of a new node at front of a given node.

2) Insertion of a new node after a given node.

3) Insertion of a new node at the end of the node.

In this tutorial, we will see how to insert a new node after a given node in Linked List. To understand this lets see the first scenario in which we have the linked list pointing a head pointer to the first node. The first node is pointing to the second one and at last, the third node is pointing to the NULL.

1) Before Insertion of the node after a given node

1) The original Linked list contains a head pointer pointing to the First Node.

2) First Node point towards the second Node.

3) The second Node point towards NULL.

2) Insertion of the node after a given node

Now if we want to insert a node after a given node of the linked list, it should be like,

1) Head is pointing to the first Node containing value 1.

2) New node next is Pointing to second Node containing value 3.

3) The first node points to the new node containing value 2.

4) The second node points to the third node containing value 4.

5) The third node containing value 4 points to null.

Now, have a look at the second scenario in which we are going to insert a node after a given node. For that thing to happen, the Head node is pointing towards the first node containing the value 1. The new node next is pointing to the second node containing the value 3. Then the first node point towards the new node containing the value2. The second node point towards the third node containing value 4. At last, the third node containing value 4 points towards NULL.

So, this is how we can manipulate the nodes to insert and get the results in the linked list. Lets see a C function on how to insert a node after a given node in the linked list.

Function to insert node after a given node of Linked List :

void insertAfter(struct node* prev_node, int dataValue)
{
  /*1. check if the given prev_node is NULL */
    if (prev_node == NULL) 
    { 
       printf("the given previous node cannot be NULL");       
       return;  
    }  
          
  /* 2. allocate new node */
    struct node* new_node =(struct node*) malloc(sizeof(struct node));
  
  /* 2. put data into new node */
    new_node->data  = dataValue;
  
    /* 4. Make next of new node as next of prev_node */
    new_node->next = prev_node->next; 
  
  /* 5. move the next of prev_node as new_node */
    prev_node->next = new_node;
}