Linked List not working for insertion

Question

I have written a linked list code to insert a element in the node. But the problem is when i want to insert first element using function, the output is coming empty. But when i insert first element inside the main function (see comment line), it gives the correct output. How to solve it ? Here is my C code:

#include<stdio.h>
#include<stdlib.h>

typedef struct node{
    int val;
    struct node *next;
}node;

void print(node *head){

    if(tem == NULL){
        printf("List is Empty\n");
        return;
    }
    node *tem= head;
    while(tem != NULL){
        printf("%d ", tem->val);
        tem= tem->next;
    }
}

void insert(node *head, int val){

    if(head == NULL){
       node *tem= malloc(sizeof(node*));
       tem->val= val;
       tem->next= NULL;
       head= tem;
       return;
    }

    node *tem= head;

    while(tem->next != NULL){
       tem= tem->next;
    }
    tem->next= malloc(sizeof(node*));
    tem->next->val = val;
    tem->next->next= NULL;
}

int main()
{
    node *head= NULL;
    /*
    head = malloc(sizeof(node*));
    head->val= 5;
    head->next= NULL;
    */

    insert(head, 15);
    print(head);

    return 0;
}

Thanks

Answer 1

Try sending the address of the head instead of head as shown below:

insert(&head, 15);

void insert(node **head, int val){

if(*head == NULL){
   node *tem= malloc(sizeof(node*));
   tem->val= val;
   tem->next= NULL;
   *head= tem;
   return;
}

This is because when you are sending the head, any changes made will be local to that function (insert in this case) and won't be reflected outside that function. Hence, you have to send the address of head (&head) so that changes made to head are reflected outside the function as well. Cheers