Linked list insertion not working for 0th index

Question

I have wrote a c program for linked list, and a function to insert a node at an index. When calling the function for index 0, The head pointer doesn't seem to be updating in the main function even though i have updated it in the insertion function. The traverse function doesn't seem to be printing the newly added element. Please help.

Code:

Node struct Main function Function for traversing and printing the list Insertion function

Output:

After insertion output is still the same

Answer 1

This is because when you insert at the beginning, you have to change the head pointer to point to the newly inserted element. For that to work, the insert_to_index function has to tell its caller (main function) what the new head is. Changing ythe value of the function parameter head inside insert_to_index is not enough, because that doesn't change the head in main.

One way to fix it is returning the new head value. To do that, change return; to return head; in insert_at_index (and change its return type from void to struct node*, and also add return head; to the end), and also change its call to head = insert_at_index(head, 0, 0); in main.

Another, alternative way to fix it is changing the parameter to struct node **head (two stars), changing head to *head within insert_at_index, and changing head to &head when insert_to_index is called from main.