How to solve this error "conflicting data types" in function declaration?

Question

https://code.sololearn.com/cFhVUHdJwGmE/?ref=app

Answer 1

No errors, create struct in before declaration.

struct node
{
int data;
struct node *next;
};
struct node *head;

void insert_at_beginning(int);
int calcsize(struct node *head);
void midinsert(struct node **ptr, int data);

Answer 2

Ferdiansyah oh yeah was in a hurry, thanks!