C infinite loop with linked list - c

Question

I am trying to make a program that initialize a singular linked list and then ask user for more data and add them at the end of current linked list. However, my programming is trapped in infinite loop.
#include <stdio.h>
#include <stdlib.h>
typedef struct linked_list
{
int data;
struct linked_list *next;
}element;
typedef element *elementptr;
void addend(elementptr *,int);
void traverse(elementptr);
int main()
{
// create a linked list
elementptr first = NULL,
last = NULL;
int input,num;
printf("Please enter first integer data: \n");
scanf("%d",&input);
//Create a linked list with user initialized data
first = (elementptr)malloc(sizeof(element));
last = first;
last -> data = input;
last -> next = NULL;
printf("Please enter number of data you want to add in the end of linked list\n");
scanf("%d",&num);
addend(&last,num);
traverse(first);
return 0;
}
void addend(elementptr *l, int num)
{
int i = 0,extradata;
while(i<num)
{
i++;
printf("Please enter a data: \n");
scanf("%d",&extradata);
(*l) -> next = (elementptr)malloc(sizeof(element));
*l = (*l) ->next;
(*l) -> data = extradata;
(*l) -> next = NULL;
}
printf("The data sets are added\n");
}
void traverse(elementptr f)
{
elementptr current;
int count = 0;
current = f;
while (current != NULL)
{
count++;
printf("The data is %d \n", current->data);
}
printf("The linked list has %d elements \n",count);
}

Answer 1

In your code
while (current != NULL)
{
count++;
printf("The data is %d \n", current->data);
}
you never change the value of current. Either it starts as NULL and the loop never executes, or it starts non-NULL and the loop runs forever.
You should add
current = current->next
after your printf to advance to the next element in the linked list.

Answer 2

current = current -> next; you are missing this statement in the while loop. Although I would suggest :
#include<stdio.h>
#include<stdlib.h>
struct linked_list
{
int number;
struct linked_list *next;
struct linked_list *prev;
};
typedef struct linked_list node;
void create(node *p);
void print(node *p);
int main()
{
node *head;
printf("---Start of the list ---\n");
printf("enter -1 to exit\n");
head = (node*)malloc(sizeof(node));
create(head);
print(head);
}
void create(node *list)
{
printf("enter the data");
scanf(" %d",&list->number);
if(list->number == -1)//Enter -1 to exit untill then keep on taking values
{
list->next=NULL;
}
else
{
list->next = (node*)malloc(sizeof(node));
create(list->next);
}
}
void print(node *list)
{
if(list->next != NULL)
{
printf("%d-->",list->number);
if((list->next->next == NULL) && (list->next->number!=-1))
printf("%d -->End of the List",list->next->number);
print(list->next);
}
}

Answer 3

In your traverse function, the current node is not pointing to next node. So the while condition while (current != NULL) will not be true and hence the while loop is running infinitely.
To fix it, current node should point to the next node (current = current->next) in the list after printing the data.
For example:
void traverse(elementptr f)
{
elementptr current;
int count = 0;
current = f;
while (current != NULL)
{
count++;
printf("The data is %d \n", current->data);
// Fix
current = current->next; // Point to next node in link list
}
}