Tutoring: example of creating a simple data structure with dynamic memory allocation and avoiding memory leaks

queue.cpp

#include <iostream>
#include "queue.hpp"

Queue::Queue():head(NULL),tail(NULL){
}

void Queue::add(int insertValue){

	Node* nextItem = new Node();
	nextItem->value = insertValue;

	if(tail != NULL)
		tail->next = nextItem;

	tail = nextItem;

	if(head == NULL)
		head = nextItem;

	return;

}

int Queue::pop(){

	Node* temp = head;
	int popValue = temp->value;

	head = head->next;

	delete temp;

	return popValue;
}

Queue::~Queue(){

	removeNode(head);

}

void Queue::removeNode(Node* node){

	if(node == NULL)
		return;

	removeNode(node->next);

	delete node;

}

queue.hpp

#pragma once

class Queue { 

	struct Node{
		Node* next;
		int value;	
	};

private:
	Node* head;
	Node* tail;
	void removeNode(Node*);

public:
 Queue();
 void add(int);
 int pop();
 ~Queue();
};

test.cpp

#include <iostream>
#include "queue.hpp"

using namespace std;

int main(){

	Queue que;

	que.add(4);
	que.add(89);
	que.add(-32);

	cout<< que.pop() <<endl; //prints 4
	cout<< que.pop() <<endl; //prints 89
	cout<< que.pop() <<endl; //prints -32

	return 0;

}