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

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

struct node *head = NULL;
struct node *current = NULL;

//insert link at the first location
void insert(int data) {
  //create a link
  struct node *link = (struct node*) malloc(sizeof(struct node));

  //link->key = key;
  link->data = data;

  //point it to old first node
  link->next = head;

  //point first to new first node
  head = link;
}

//display the list
void printList() {

  struct node *ptr = head;

  printf("\n[head] =>");
  //start from the beginning
  while(ptr != NULL) {
    printf(" %d =>",ptr->data);
    ptr = ptr->next;
  }

  printf(" [null]\n");
}

int main() {
  fprintf(stdout, "initial:\n");
  printList();
  insert(10);
  fprintf(stdout, "after first insertion:\n");
  printList();
  insert(20);
  fprintf(stdout, "after second insertion:\n");
  printList();
  insert(30);
  insert(1);
  insert(40);
  insert(56);
  printList();

  return 0;
}