/*
	Stack a.k.a. LIFO

	http://en.wikipedia.org/wiki/Stack_(computing)
	
	(c) BruXy -- http://bruxy.regnet.cz/fel/

   */

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

/*********************
 * Globalni promenne *
 *********************/

typedef struct stack{
	int data;
	struct stack *odkaz;
} STACK;

/*********************
 *     Funkce        *
 *********************/

STACK *create(void){
	STACK *test;

	test = ( (STACK *) malloc(sizeof(STACK)) );
	if(test==NULL){
		printf("Malo pameti!\n");
		return NULL;
	}
	test->odkaz=NULL;

	return test;
}

/* Vrazi cislo do zasobniku a zvetsi ho o jeden prvek */

STACK *push(int cislo, STACK *stack)
{
	STACK *s_novy;
	
	s_novy = create();
	s_novy->data = cislo;
	s_novy->odkaz = stack;

	return s_novy;
}

/* Vymaze posledni cislo zasobniku a nastavi novou adresu vrcholu */

STACK *pop(STACK *stack)
{
	STACK *s_temp;

	if(stack->odkaz==NULL){
		printf("Zasobnik je prazdny!\n");
		return NULL;
	}
	
	s_temp = stack;
	free(s_temp);
	
	return stack = stack->odkaz;
}

void free_data(STACK *stack){
	for( ; stack->odkaz != NULL; stack = stack->odkaz)
    	free(stack);
	return;
}

void print_data(STACK *stack){
	for( ; stack->odkaz != NULL; stack = stack->odkaz)
		printf("%p = %d \n", (void *) stack, stack->data);
	return;
}

/*********************
 *       Main        *
 *********************/

int main(){
	int cislo, size;
	int citac = 0;

	STACK *s_top;

	printf("Kolik prvku ma obsahovat stack?: ");
	scanf("%d", &size);
	
	/* Ukazatel na zacatek */
	s_top = create();
		
	/* Vsechny ukazuji na stejnou adresu */

	for(;;)
	{
		if(citac == size) break;
		printf("Zadej cislo %d. : ", citac+1);
		scanf("%d", &cislo);
		printf("Ukladam %d na adresu %p.\n", cislo, (void *) s_top);

		s_top = push(cislo, s_top);
		printf("Addr -> %p.\n", (void *) s_top);
		putchar('\n');
		citac++;
	}

	/* Vypsani obsahu celeho stacku */
	printf("Vypis naplnenych dat.\n");

	print_data(s_top);
	
	printf("\nKolik mam vymazat prvku?:");
	scanf("%d", &cislo);
	citac = 0;
	
	for(;;)
	{
		if(citac == cislo) break;
		if(pop(s_top) != NULL)
			s_top = pop(s_top);
		else 
			break;
		
		citac++;	
	}
	
	print_data(s_top);

	/* Na zaver po sobe uklidime */
	
	free_data(s_top);

	return 0;
}