Design a method for keeping two stacks within a single linear array so that neither stack overflows until all of memory is used and an entire stack is never shifted to a different location within the array.
Write usual stack routines to manipulate the two stacks.
Hint : The two stacks grow towards each other. In your function, use an extra integer parameter to identify the stack to be used.

#define N 20
typedef int  element;
typedef struct  {
	element data[N]; 
	int top1,top2;
} stack;

stack CreateStack()
{
	stack p;
	p.top1 = -1;
	p.top2=N;
	return p;
}

int Push(stack *p, element e, int n)
{
	if (isFullStack(*p)) return 0;
	if(n==1)
		p->data[++p->top1]=e;
	else
		p->data[--p->top2] = e;
	return 1;
}

int Pop(stack *p, int n)
{
	if (isEmptyStack(*p,n)) return 0;
	if(n==1)
		p->top1--;
	else
		p->top2++;
	return 1;
}

int Top(stack p, element *e, int n)
{
	if (isEmptyStack(p,n)) return 0;
	if(n==1)
		*e = p.data[p.top1];
	else
		*e = p.data[p.top2];
	return 1;
}

int isEmptyStack(stack p, int n)
{
	if(n==1)
		return (p.top1 == -1);
	if(n==2)
		return (p.top2==N);
}

int isFullStack(stack p)
{
	return (p.top1+1 == p.top2);
}