Question

Hi i have a problem with my stack data structure program. It seems that when i define the size of my array/the imaginary size of array just to call it through a loop the size i defined or specified by the user is being depleted or somewhat edited when i enter a data or push.

For ex. i entered 5 for the size and choose push and then add 2. It is working properly. But if i choose to push data again, it is now passing to the size variable. I do not know understand what is happening…

#include <stdio.h>
#include <ctype.h>
#include <conio.h>
#include <string.h>
#include <stdlib.h>
#define p printf
#define s scanf

int top;
int ar[1];
int size;

main()
{
    void push();
    int opt, num;
    char cont[] = { 'y' };
    clrscr();

    p("Stacking Program");
    p("\n\nData Size: ");
    s("%d", &size);
    p("\n");

    while((cont[0] == 'y') || (cont[0] == 'Y'))
    {
        clrscr();
        p("Stacking Program");
        p("\n\nData Size: %d\n\n", size);
        p("MAIN MENU\n1. Pop\n2. Push\n3. Pick\n4. View\nChoose: ");
        s("%d", &opt);
        p("\n");

        switch(opt) {
            case 1:
                pop();
                break;
            case 2:
                if(top > size)
                {
                    p("You can't push more data");
                }
                else
                {
                    p("Enter data for Data[%d]: ", top);
                    s("%d", &num);
                    push(num);
                }
                break;
            case 3:
                pick();
                break;
            case 4:
                view();
                break;
            default:
                p("Your choice is not in the list.");
                break;
        }

        p("\n\nDo you want continue\(Y\/N\)?");
        s("%s", &cont[0]);
    }
}

pop()
{
    int a;
    if(top < 0)
    {
        p("Stack empty.");
        return 0;
    }
    else
    {
        a = ar[top];
        p("\(Data[%d] = %d\) removed.", top, a);
        top--;
    }
}
void push(int b)
{
    top++;
    ar[top] = b;
}
pick()
{
    if(top < 0)
    {
        p("Nothing to display.");
        return 0;
    }
    else
    {
        p("\(Data[%d] = %d\) is the last data.", top, ar[top]);
    }
}
view()
{
    int i;
    if(top < 0)
    {
        p("Nothing to display.");
        return 0;
    }
    else
    {
        for(i = 1; i < (top + 1); i++)
        {
            p("Data[%d] = %d\n", i, ar[i]);
        }
    }
}

Answer 1

You need to define the size of the array at runtime, using the size entered by the user.
instead of:

int top;
int ar[1];
int size;

…

int top = -1;
int *ar = NULL;
int size = 0;

and then after getting size from the user:

   if ( size > 0 )
   {
      ar = malloc(size * sizeof(int));
      if ( ar == NULL )
      {
         printf("ERROR: malloc() failed\n");
         exit(2);
      }
   }
   else
   {
      printf("ERROR: size should be positive integer\n");
      exit(1);
   }


   ....
      p("\n\nDo you want continue(Y/N)?");
      s("%s", &cont[0]);
   }
   free(ar);


} // end of main

I think the for loop in view() should be:

 for(i = 0 ; i <= top ; i++)

also

case 2:
    if ( top == ( size - 1 ))