09 Insert a new node before a particular node in LInked List

         Insert a new node before a particular node

                                          

                              

             

Figure 5. Insert node before a  Node.

Logic:

Before calling insert_before function in main call search function and find out nxt pointer by equating data.

Prepare a new_node of desired data and cursor->next pointer

Then assign cursor->next to new_node.  

Main Function code:

node* nxt=NULL;
printf("\n Enter data of  node before which you want to add a node:");
scanf("%d",&data);

nxt=search(head,data);
printf("\n Enter data for adding a new node before a node:");
scanf("%d",&data);
head=insert_before(head,data,nxt);
display(head);

C function for insert before function:-

node* insert_before(node *head, int data, node* nxt)

{

    if(nxt == NULL || head == NULL)

        return NULL;

     if(head == nxt)      //If nxt node is head then simply prepend the data

    {

        head = prepend(head,data);

        return head;

    }

// search previous pointer by equating cursor->next with nxt

    node *cursor = head;

    while(cursor != NULL)

    {

        if(cursor->next == nxt)

            break;

        cursor = cursor->next;

    }

 //if cursor is not NULL then create a node having create(data,cursor->next)

    if(cursor != NULL)

    {

        node* new_node = create(data,cursor->next);

        cursor->next = new_node;

        return head;

    }

    else

    {

        return NULL;

    }
}