N stack 1 Array

Implement N stacks using constant sized array(space). Until the array is completely filled, I should be able to push elements to any one of the N stacks.(i.e.)Do not reserve space for the stacks. And I should also be able to pop elements from any stack.

Sounds very tricky. The idea is :

Keep an array S of N pointer, where each S_i.top will point to the top of the corresponding stack. And one global pointer gptr, which points to the next free location in the array. Now follow the steps:

Now implement Push(stackToPush) and pop(StackToPop) as follows :

Push(x, Si) //pushing x in Stack Si.
{
if(gptr > sizeof(Arr))
{
// To Be Added -- explained below
}
Arr[gptr].data = x;
Arr[gprt].prev = Si.top;
Si.top = gptr;
gptr++;
}


Pop(Si)
{
T data = Arr[Si.top].data; //T is data type
Si.top = Arr[Si.top].prev;
return data;
}

I would suggest that you try a very detailed dry-run with a little visual aid for this.