arnuld
6/1/2011 10:57:00 AM
It works fine. I have explained everything in comments. As usual, all
comments for improving the program are welcomed :)
/* A stack (LIFO) implemented using doubly linked list for learning data
structures :) .
* Definiton of stack and operations on it are taken from Data Structures
and Algorithms by Aho, Hopcraft and Ullman
* page 67, section 2.3
*
* VERSION 0.0
*/
#include <stdio.h>
#include <stdlib.h>
enum {
VALUE_SUCCESS = 0, VALUE_ERROR = 1,
VALUE_TRUE = 1, VALUE_FALSE = 0
};
struct stack_node
{
int num;
struct stack_node* next;
struct stack_node* prev;
};
struct stack_list
{
struct stack_node* head;
};
struct stack_node* top(struct stack_list* s);
void pop(struct stack_list* s);
int push(struct stack_list* s, int i);
void makenull(struct stack_list* s);
int empty(struct stack_list* s);
void print_list(struct stack_list* s);
void print_node(struct stack_node* p);
int main(void)
{
struct stack_list* s = malloc(1 * sizeof *s);
if(NULL == s)
{
fprintf(stderr, "IN: %s @%d: Invalid Args!\n", __FILE__, __LINE__);
return EXIT_FAILURE;
}
print_list(s);
push(s,1);
print_list(s);
printf("empty = %d\n", empty(s));
push(s,2);
push(s,3);
print_list(s);
printf("empty = %d\n", empty(s));
makenull(s);
printf("empty = %d\n", empty(s));
print_list(s);
return EXIT_SUCCESS;
}
int push(struct stack_list* s, int i)
{
int ret = VALUE_ERROR;
if(NULL == s)
{
fprintf(stderr, "IN: %s @%d: Invalid Args!\n", __FILE__, __LINE__);
ret = VALUE_ERROR;
}
else
{
struct stack_node* p = malloc(1 * sizeof *p);
if(NULL == p)
{
fprintf(stderr, "IN: %s @%d: Out of Memory!\n", __FILE__,
__LINE__);
ret = VALUE_ERROR;
}
else
{
p->num = i;
p->next = NULL;
p->prev = NULL;
if(NULL == s->head)
{
printf("Adding first element\n");
s->head = p;
}
else
{
/* struct stack_node* h = s->head; */
p->next = s->head;
s->head->prev = p;
s->head = p;
}
ret = VALUE_SUCCESS;
}
}
return ret;
}
void pop(struct stack_list* s)
{
if(NULL == s || NULL == s->head)
{
printf("Nothing to pop\n");
}
else
{
struct stack_node* p = s->head;
s->head = s->head->next;
if(s->head) s->head->prev = NULL;
free(p);
}
}
void makenull(struct stack_list* s)
{
if(NULL == s)
{
fprintf(stderr, "IN: %s @%d: Invalid Args!\n", __FILE__, __LINE__);
}
else
{
while(s->head)
{
printf("Makenull removing: %d\n",s->head->num);
pop(s);
}
}
}
int empty(struct stack_list* s)
{
int ret = VALUE_FALSE;
if(NULL == s)
{
fprintf(stderr, "IN: %s @%d: Invalid Args!\n", __FILE__, __LINE__);
ret = VALUE_FALSE;
}
else if(NULL == s->head)
{
ret = VALUE_TRUE;
}
else
{
ret = VALUE_FALSE;
}
return ret;
}
/* ----------------------- my won fucntions for printing
-------------------------- */
void print_list(struct stack_list* s)
{
struct stack_node* p = s->head;
for(; p; p = p->next)
{
print_node(p);
}
printf("----------------------------------------------------\n\n");
}
void print_node(struct stack_node* p)
{
printf("p->num = %d\n", p->num);
}
====================== OUTPUT ===========================
[arnuld@dune C]$ gcc -ansi -pedantic -Wall -Wextra stack_dl.c
[arnuld@dune C]$ ./a.out
----------------------------------------------------
Adding first element
p->num = 1
----------------------------------------------------
empty = 0
p->num = 3
p->num = 2
p->num = 1
----------------------------------------------------
empty = 0
Makenull removing: 3
Makenull removing: 2
Makenull removing: 1
empty = 1
----------------------------------------------------
[arnuld@dune C]$
--
www.lispmachine.wordpress.com
find my email-ID @above blog