WANTED: To write an array implementation of Stack.
WHAT I GOT: It works fine.
I think program is still little too complex. Any ideas to improve ?
/* Array implementation of Stack - Aho, Hopcraft and Ullman, page 68-70
* section 2.3. We will add element at the bottom and we will grow the
* stack to top. top_index will keep track of index where element was
* added as latest. We will use top_index to push/pop elements.
*
* VERSION 0.0.
*
*/
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
enum {
SIZE_NAME = 10, SIZE_ARR = 3,
VAL_SUCC = 0, VAL_ERR = 1
};
struct elm
{
int num;
char name[SIZE_NAME+1];
};
struct elm_stack
{
int top_index;
struct elm* arr[SIZE_ARR];
};
int push(struct elm_stack* , struct elm* );
void pop(struct elm_stack* );
struct elm_stack* stack_init(void);
void print_stack(struct elm_stack* );
struct elm* get_element(const char* c, int n);
int main(void)
{
struct elm_stack* s = stack_init();
struct elm* e0 = get_element("comp", 2);
struct elm* e1 = get_element("lang", 1);
struct elm* e2 = get_element("c", 0);
int ret_elem = push(s, e0);
if(VAL_ERR == ret_elem)
{
printf("IN: %s @%d: Memory Full\n", __FILE__, __LINE__);
free(e0);
}
ret_elem = push(s, e1);
if(VAL_ERR == ret_elem)
{
printf("IN: %s @%d: Memory Full\n", __FILE__, __LINE__);
free(e1);
}
ret_elem = push(s, e2);
if(VAL_ERR == ret_elem)
{
printf("IN: %s @%d: Memory Full\n", __FILE__, __LINE__);
free(e2);
}
print_stack(s);
printf("-----------------------------------------\n\n");
pop(s);
print_stack(s);
printf("-----------------------------------------\n\n");
pop(s);
print_stack(s);
printf("-----------------------------------------\n\n");
pop(s);
print_stack(s);
return EXIT_SUCCESS;
}
int push(struct elm_stack* s, struct elm* e)
{
int ret;
if(NULL == s || NULL == e)
{
printf("IN:%s @%d Invalid Args!\n", __FILE__, __LINE__);
ret = VAL_ERR;
}
else if(s->top_index == 0)
{
ret = VAL_ERR;
}
else
{
--(s->top_index);
/* printf("s->top_index = %d\n", s->top_index); */
s->arr[s->top_index] = e;
/* printf("%s = %d\n", e->name, e->num); */
ret = VAL_SUCC;
}
return ret;
}
void pop(struct elm_stack* s)
{
if(NULL == s)
{
printf("IN:%s @%d: Invalid Args!\n", __FILE__, __LINE__);
}
else if(SIZE_ARR <= s->top_index)
{
printf("Nothing to pop()\n");
}
else
{
struct elm* e = s->arr[s->top_index];
free(e);
++(s->top_index);
}
}
struct elm_stack* stack_init(void)
{
int idx;
struct elm_stack* p = malloc(1 * sizeof *p);
if(NULL == p)
{
printf("IN: %s @%d: Out of Memory!\n", __FILE__, __LINE__);
}
else
{
p->top_index = SIZE_ARR;
for(idx = 0; idx < SIZE_ARR; ++idx) p->arr[idx] = NULL;
}
return p;
}
struct elm* get_element(const char* c, int n)
{
struct elm* p = malloc(1 * sizeof *p);
if(NULL == p)
{
printf("IN:%s @%d: Out of Memory!\n", __FILE__, __LINE__);
}
else if(SIZE_NAME < strlen(c))
{
printf("IN: %s @ %d: ", __FILE__, __LINE__);
printf("Name too big, Not adding element\n");
free(p);
p = NULL;
}
else
{
p->num = n;
strcpy(p->name,c);
}
return p;
}
void print_stack(struct elm_stack* s)
{
if(NULL == s)
{
printf("IN:%s @%d: Invalid Args!\n", __FILE__, __LINE__);
}
else
{
int idx = SIZE_ARR - 1;
struct elm* e;
/*printf("idx %d, top_index = %d\n", idx, s->top_index); */
for(; (idx >= 0) && (idx >= s->top_index); --idx)
{
/*printf("idx %d, top_index = %d\n", idx, s->top_index);*/
e = s->arr[idx];
printf("%s = %d\n", e->name, e->num);
}
}
}
=================== OUTPUT ========================
[arnuld@dune C]$ gcc -ansi -pedantic -Wall -Wextra lifo-array.c
[arnuld@dune C]$ ./a.out
comp = 2
lang = 1
c = 0
-----------------------------------------
comp = 2
lang = 1
-----------------------------------------
comp = 2
-----------------------------------------
[arnuld@dune C]$
--
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