#include "list.h"


/* Inserts number at the beginning of list L. L points to
 * the first element of the list - a dummy cell storing the
 * number of cells in the list.
 */
void insert_list(int number, List L)
{
	List e;

	// allocate space for a cell and store number in it
	e = (List) malloc(sizeof(Cell)); 
	e->element = number;

	// insert the cell at teh beginning of L
	e->next = L->next;
	L->next = e;
	(L->element)++; // increment the counter in dummy cell
}


/* Searches for occurance of number in list L. Returns a pointer
 * to thecell just before the cell containing number, if it exists.
 * Returns NULL otherwise.
 */
List search_list(int number, List L)
{
	if (L->next == NULL) // number does not exists in the list
		return NULL;

	if ((L->next)->element == number) // found it!
		return L;

	// number is not in the next cell. Search remaining list for it
	return search_list(number, L->next);
}


/* Deletes the cell containing number in the list L, if it exists.
 * Returns -1 otherwise.
 */
int delete_list(int number, List L)
{
	List x, y;

	x = search_list(number, L); // look for number
	
	if (x == NULL) // number does not exist
		return -1;

	// Number is present in the next cell y
	y = x->next; 

	// remove y
	x->next = y->next;
	free(y);

	// Update the counter
	(L->element)--;

	return 1;
}

/* Prints the elements of list L */
void print_list(List L)
{
	printf("List has %d numbers\n", L->element);
	for (L = L->next; L != NULL; L = L->next)
		printf("%d ", L->element);
	printf("\n");
}