cannot use private part [closed] - c++

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I had an exam and they asked about queues. I am wonder how a reverse method can be written without using any private part of the header file given. So the method must be written by using only public part of the file. Also you cannot create a new Queue, or delete the queue existing already. You cannot use inheritance, interface etc. Also the method is required to work in O(N) time complexity. It is too much required and I could not find a solution for it.
Header file is :
#include <iostream>
using namespace std;
class Queue
{
public:
Queue(); // Class constructor
~Queue(); // Class destuctor
void ClearQueue(); // Remove all items from the queue
bool Enqueue(int newItem); // Enter an item in the queue
int Dequeue(); // Remove an item from the queue
bool isEmpty(); // Return true if queue is empty
private:
struct Node(){
Node *next;
int item;
};
Node *front;
Node *back;
};
//and the prototype of the method wanted :
bool reverse(){
}

Answer 1

You could write a recursive function. Add the following function to your class:
bool reverse() {
if (this->isEmpty())
return true;
int value = this->Dequeue();
this->reverse();
this->Enqueue(value);
return true;
}
If you don't want the function to be a method of the class Queue and you have a global Queue-object queue, you could also write a global function like this:
bool reverse() {
if (queue.isEmpty())
return true;
int value = queue.Dequeue();
queue.reverse();
queue.Enqueue(value);
return true;
}
If you don't have a global Queue-object, you will have to pass the queue as parameter, see:
bool reverse(Queue& queue) {
if (queue.isEmpty())
return true;
int value = queue.Dequeue();
queue.reverse(queue);
queue.Enqueue(value);
return true;
}