Implementation of stack using an array
In this section we shall show how stacks can be implemented using arrays. Consider a
situation where goods of varying quality are being produced in a factory. Every batch of
goods has the same quality. As the items are being produced, we want to store the
information regarding the number of items produced and the quality of that batch ( ‘H’ for
high quality, ‘G’ for good quality, ‘A’ for average quality etc.) on a stack using PUSH
function. To deliver the items to a client, we want to use the POP function. The POP function
is supposed to remove the items from the stack. We are also interested to find out if the stack
is full or empty at any point in time.
Let us consider the following structure where we have two arrays serving as stacks for
“items” and “quality”. The variable top indicates the position of the last item in an array.
The variable MAXSTACK defines the maximum size of the stack.
We use the ‘arrow’ symbol to indicate component of a structure that is being referenced
through a pointer. Thus if *produce is a pointer to the structure in any function call then we
can write
produce-> top to denote (*produce ).top
Let MAXSTACK denote the maximum size of the stack.
#define MAXSTACK 20
//Here is the structure declaration:
struct arraystack {
int items[MAXSTACK];
char quality[MAXSTACK];
int top;
};
//Function definitions
//Precondition: Enter a valid pointer name which should not be NULL
//Postcondition: Returns 1 if stack is empty , otherwise returns 0.
int isEmpty( struct arraystack *produce )
{
return ( produce-> top < 0 );
}
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