Stack of strings - c

Question

Hi i have program here that accept int as value. i wanted to translate it to accept strings in array then. i have read about using struct but i couldnt get into it. i hope someone can help me getting into that without using struct i dont know where to start i want to keep this lines of code.
#include <stdio.h>
#include <ctype.h>
#include <conio.h>
#include <string.h>
#include <stdlib.h>
int top = 0;
int *stack = NULL;
int size = 0;
main()
{
int opt, num;
char cont[] = { 'y' };
clrscr();
/* <start Declaring Stack Size { */
printf("Stacking Program");
printf("\n\nData Size: ");
scanf("%d", &size);
printf("\n");
/* } end> */
/* <start Allocates size of stack { */
if(size > 0)
{
stack = malloc(size * sizeof(int));
if(stack == NULL)
{
printf("ERROR: malloc() failed\n");
exit(2);
}
}
else
{
printf("ERROR: size should be positive integer\n");
exit(1);
}
/* } end> */
while((cont[0] == 'y') || (cont[0] == 'Y'))
{
clrscr();
/* <start Main Menu { */
printf("Stacking Program");
printf("\n\nData Size: %d\n\n", size);
printf("MAIN MENU\n1. Pop\n2. Push\n3. Pick\n4. View\nChoose: ");
scanf("%d", &opt);
printf("\n");
switch(opt) {
case 1:
pop();
break;
case 2:
if(top==size)
{
printf("You can't push more data");
}
else
{
printf("Enter data for Stack[%d]: ", top+1);
scanf("%d", &num);
push(num);
}
break;
case 3:
pick();
break;
case 4:
view();
break;
default:
printf("Your choice is not on the list.");
break;
}
/* } end> */
printf("\n\nDo you want continue\(Y\/N\)?");
scanf("%s", &cont[0]);
}
free(stack);
}
pop()
{
int a;
loading();
if(top <= 0)
{
printf("Stack empty.");
return 0;
}
else
{
top--;
a=stack[top];
printf("\(Stack[%d] = %d\) removed.", top+1, a);
}
}
push(int a)
{
stack[top]=a;
top++;
loading();
}
pick()
{
loading();
if(top <= 0)
{
printf("Nothing to display.");
return 0;
}
else
{
printf("\(Stack[%d] = %d\) is the last data.", top, stack[top-1]);
}
}
view()
{
int i;
loading();
if(top <= 0)
{
printf("Nothing to display.");
return 0;
}
else
{
for(i=0;i<top;i++)
{
printf("Stack[%d] = %d\n", i+1, stack[i]);
}
}
}
loading()
{
float i, x;
float load;
int loadarea[] = { 5000, 10000, 15000, 20000, 25000, 30000 };
int percentLoad;
x=0;
load=0;
percentLoad = loadarea[random(5)];
gotoxy(26,11);
printf("[");
for(i=0;i<25;i++)
{
x = i+27;
gotoxy(x, 11);
printf("=");
delay(percentLoad);
gotoxy(51,11);
printf("]");
gotoxy(53,11);
load=(i/25)*104.5;
if(load>100)
load = 100.00;
printf("%.2f\%",load);
}
delay(60000);
for(i=0;i<60;i++) {
printf("\b \b");
}
printf("\n");
}

Answer 1

Easiest way is to convert your stack to store char* instead of int.
char **stack;
stack = malloc( size * sizeof(char*) );
Now, your push operation will accept a char* from some buffer that is storing the string that was just input, duplicate it with strdup, and store that new pointer in the stack.
typedef enum {
STACK_MEM_ERROR = -1,
STACK_FULL = 0,
STACK_OK = 1
} StackStatus;
StackStatus push(const char *str)
{
char *newstr;
if( top >= size ) return STACK_FULL;
newstr = strdup(str);
if( newstr == NULL ) return STACK_MEM_ERROR;
stack[top++] = newstr;
return STACK_OK;
}
When you pop a string, you just get a pointer.
char *pop()
{
if( top == 0 ) return NULL;
return stack[--top];
}
You are responsible for freeing that memory when you are finished with the pointer (by calling free).
char * val;
while( NULL != (val = pop()) )
{
printf( "I popped: %s\n", val );
free(val);
}