Stack.cpp

#include "Stack.h"

Stack::Stack() : topPtr(NULL) {

}

// copy constructor
Stack::Stack(const Stack& aStack) {

	if (aStack.topPtr == NULL)
		topPtr = NULL;  // original stack is empty

	else {
		// copy first node
		topPtr = new StackNode;
		topPtr->item = aStack.topPtr->item;

		// copy rest of stack
		StackNode* newPtr = topPtr;
		for (StackNode* origPtr = aStack.topPtr->next;
			origPtr != NULL;
			origPtr = origPtr->next) {
			newPtr->next = new StackNode;
			newPtr = newPtr->next;
			newPtr->item = origPtr->item;
		}
		newPtr->next = NULL;
	}
}

// destructor 
Stack::~Stack() {

	// pop until stack is empty
	while (!isEmpty())
		pop();

}


bool Stack::isEmpty() const {

	return topPtr == NULL;

}

bool Stack::pop() {

	if (isEmpty())
		return false;

	// stack is not empty; delete top
	else {
		StackNode* temp = topPtr;
		topPtr = topPtr->next;

		// return deleted node to system
		temp->next = NULL;  // safeguard
		delete temp;
		return true;
	}
}

bool Stack::pop(StackItemType& stackTop) {

	if (isEmpty())
		return false;

	// not empty; retrieve and delete top 
	else {
		stackTop = topPtr->item;
		StackNode* temp = topPtr;
		topPtr = topPtr->next;

		// return deleted node to system
		temp->next = NULL;  // safeguard
		delete temp;
		return true;
	}
}


bool Stack::push(const StackItemType newItem) {

	// create a new node
	StackNode* newPtr = new StackNode;

	// set data portion  of new node
	newPtr->item = newItem;

	// insert the new node
	newPtr->next = topPtr;
	topPtr = newPtr;

	return true;
}

bool Stack::getTop(StackItemType& stackTop) const {

	if (isEmpty())
		return false;

	// stack is not empty; retrieve top
	else {
		stackTop = topPtr->item;
		return true;
	}

}