Question

In C programming,

Modify the function Pop in the example so that it has the signature

                                                bool Pop(LIST *list, char *c)

and returns false if the list is empty and returns true if not empty. On success it returns the value removed from the stack in the variable c. Modify the function CheckForBalance to accommodate this change and rerun the test program giving the same output as in the example.

:here is the CheckForBalance example code, the rest of the code is just to  verify that a bracket string is balanced:

bool CheckForBalance(LIST* list, char* str, int size)
{
   char c;
   bool retval = true;

   for (int i = 0; i < size && retval; i++)
   {
       switch (str[i])
       {
       case '(':
       case '{':
       case '[':
           Push(list, str[i]);
           break;

       case ')':
       case '}':
       case ']':
           if (IsEmpty(list))
           {
               retval = false;
           }
           else
           {
               c = Pop(list);
               if (!IsMate(c, str[i]))
               {
                   retval = false;
               }
           }
           break;

       default:
           retval = false;
           break;
       }
   }

   return retval;
}

Answer 1

# FOLLOWING IS THE MODIFIED function Pop AS ASKED IN QUESTION ,

(Please read comments mentioned in code to understand the code better.)

--------------------------------------------------------

bool Pop(LIST *list, char *c)
{
   if (IsEmpty(list))
        {
               return false;
        }
   else
   {
      
       /* No info about LIST data structure is given, hence it is assumed that list contains varaible 'data'. */
       /* LIST data structure can be implemented using linked list. In C, struct can be defined... */
        /* ... for implementation of singly linked list */
       /* Char variable c pointed by pointer c stores value of 'data' element to be poped present in list.*/
      *c = list->data;

       list = list->next; /* Parenthesis present in list is poped for balancing. */
       return true;
   }

}

---------------------------------------------------------------------------

# FOLLOWING IS THE function CheckForBalanceTO ACCOMODATE MODIFIED POP FUNCTION,

bool CheckForBalance(LIST* list, char* str, int size)
{
char c;
c = 'a';   /* Initialized character variable c with dummy value to avoid any errors regarding initialization*/
bool retval = true;

   for (int i = 0; i < size && retval; i++)
   {
       switch (str[i])
       {
       case '(':
       case '{':
       case '[':
           Push(list, str[i]);
           break;

       case ')':
       case '}':
       case ']':
           if (IsEmpty(list))
           {
               retval = false;
           }
           else
           {
               /*Returns boolean values true or false which is stored in retval variable */
               /*address of char c variable is passed using call by reference */

               retval=Pop(list, &c);      

               /* After execution of above line, char variable c now has the poped element stored.*/
             

               if (!IsMate(c, str[i]))
               {
                   retval = false;
               }
           }
           break;

       default:
           retval = false;
           break;
       }
   }

   return retval;
}

--------------------------------------------------------

Hence all the required modifications have been answered as asked in the question with coments :)