Question

I had a certain query regarding a question I was asked earlier.

I was given this function prototype void StackPop(NodeType *Top) and was told modify the top of the stack without access to the stack object. StackPop function here is a global function and not a member function of the Stack class. After popping, Top should point to the new value of Top element.

As a solution, popping the top of the stack in such a case would only be possible if we pass the address of the top node of the stack to the function while calling. eg: StackPop(&address);
To modify the top of the stack

NodeType* temp;
temp = top;
*top = (*top)->next;
delete temp;

Is this the simple answer to the question or is something else the case that has to be taken care of?

Answer 1

Yes, this is a valid simple answer to the question, with three caveats:

1. temp = top should read temp = *top;
2. you might want to gracefully handle the case where *top is NULL (rather than just dereferencing the NULL pointer);
3. this solution is of course incompatible with the prototype you were given [void StackPop(Node *Top)] as it would take Node** as its argument.

The only other remark that I have is that StackPop sounds like it ought to be a member function rather than a free function.