#include <stdio.h>

typedef struct _node {
   char element;
   struct _node *next;
} node;

typedef node *olist;

olist init ()
{
   olist L;

   /* Create the dummy node */
   L = (node *)malloc(sizeof(node));
   L -> element = '\0';
   L -> next = NULL;
   return L;
}

olist insert ( olist L , char ch , int pos )
{
   int i;
   node *p, *n;

   if (pos < 0) {
      fprintf(stderr, "insert: Invalid index %d\n", pos);
      return L;
   }
   p = L;
   i = 0;
   while (i < pos) {
      p = p -> next;
      if (p == NULL) {
         fprintf(stderr, "insert: Invalid index %d\n", pos);
         return L;
      }
      ++i;
   }
   n = (node *)malloc(sizeof(node));
   n -> element = ch; 
   n -> next = p -> next;
   p -> next = n;
   return L;
}

olist delete ( olist L , int pos )
{
   int i;
   node *p;

   if (pos < 0) {
      fprintf(stderr, "delete: Invalid index %d\n", pos);
      return L;
   }
   p = L;
   i = 0;
   while ((i < pos) && (p -> next != NULL)) {
      p = p -> next;
      ++i;
   }
   if (p -> next == NULL) {
      fprintf(stderr, "delete: Invalid index %d\n", pos);
      return L;
   }
   p -> next = p -> next -> next;
   return L;
}

int isPresent ( olist L , char ch )
{
   int i;
   node *p;

   i = 0;
   p = L -> next;
   while (p != NULL) {
      if (p -> element == ch) return i;
      p = p -> next;
      ++i;
   }
   return -1;
}

char getElement ( olist L , int pos )
{
   int i;
   node *p;

   i = 0;
   p = L -> next;
   while ((i < pos) && (p != NULL)) {
      p = p -> next;
      ++i;
   }
   if (p == NULL) {
      fprintf(stderr, "getElement: Invalid index %d\n", pos);
      return '\0';
   }
   return p -> element;
}

void print ( olist L )
{
   node *p;

   p = L -> next;
   while (p != NULL) {
      printf("%c", p -> element);
      p = p -> next;
   }
}

int main ()
{
   olist L;

   L = init();
   L = insert(L,'a',0);
   printf("Current list is : "); print(L); printf("\n");
   L = insert(L,'b',0);
   printf("Current list is : "); print(L); printf("\n");
   L = delete(L,5);
   printf("Current list is : "); print(L); printf("\n");
   L = insert(L,'c',1);
   printf("Current list is : "); print(L); printf("\n");
   L = insert(L,'b',3);
   printf("Current list is : "); print(L); printf("\n");
   L = delete(L,2);
   printf("Current list is : "); print(L); printf("\n");
   L = insert(L,'z',8);
   printf("Current list is : "); print(L); printf("\n");
   L = delete(L,2);
   printf("Current list is : "); print(L); printf("\n");
   printf("Element at position 1 is %c\n", getElement(L,1));
}