编写一个 C 程序，在循环单链表的开头插入一个节点。

c
#include
#include
void beg_insert(int);
struct node
{
int data;
struct node *next;
};
struct node *head;
void main ()
{
int choice,item;
do
{
printf("\nEnter the item which you want to insert?\n");
scanf("%d",&item);
beg_insert(item);
printf("\nPress 0 to insert more ?\n");
scanf("%d",&choice);
}while(choice == 0);
}
void beg_insert(int item)
{

struct node *ptr = (struct node *)malloc(sizeof(struct node));
struct node *temp;
if(ptr == NULL)
{
printf("\nOVERFLOW");
}
else
{
ptr -> data = item;
if(head == NULL)
{
head = ptr;
ptr -> next = head;
}
else
{
temp = head;
while(temp->next != head)
temp = temp->next;
ptr->next = head;
temp -> next = ptr;
head = ptr;
}
printf("\nNode Inserted\n");
}
}