从后到前显示通过链接列表实现的队列

Question

I am currently working on a project for class that requires me to implement a queue with a linked list without using a library. So far my project is working perfectly but when I push_back() 1, 3, 5, 7 the screen displays it with the front of the queue on the left. I would prefer it to look Rear on the left such as REAR 7 5 3 1 FRONT. What exactly am I missing here that would help me do this?

#include "queue.h"
#include <iostream>
Queue::Queue()
{
    queue_size = 0;
    front = 0;
    rear = 0;
}
Queue::~Queue()
{
    delete front;
    delete rear;
}

void Queue::push_back(int x)
{
    node * q = new node;
    q->data = x;
    q->next = 0;

    if(this->isEmpty())
    {
        front = q;
        front ->next = 0;
        rear = front;
    }
    else
    {
        rear->next = q;
        rear = rear->next;
        rear->next = 0;
    }
    queue_size = queue_size + 1;
}

void Queue::pop_front(int &num)
{
    node * temp;
    num = front->data;
    temp = front;
    front = front ->next;
    delete temp;
    queue_size = queue_size - 1;



}
bool Queue::isEmpty()
{
    if(front == 0)
        return true;

    else
        return false;

}

int Queue::ret_size()
{
    return queue_size;
}

void Queue::display()
{
   node * temp;
   temp = front;

   for(int i = 0; i < queue_size; i++)
   {
       std::cout<<temp->data<< " ";
       temp = temp->next;
   }
   std::cout<<"\n";
}

Answer 1

If you are comfortable with recursion, and have some faith that your system has sufficient stack for the size of Queues you plan, this can work.

void Queue::display(void)
{
   node* temp;
   temp = front;

   if(temp)
      temp->displayR();

   std::cout<<"\n";
}

void Queue::displayR(void)
{
   if(m_next) 
      m_next->displayR(); // spin down to end of queue

   // now display the current data
   std::cout << data << "  "; // report end of queue first
}

FYI: on ubuntu 12.04 and 4 Gig of ram, I believe I do not experience stack overflows until more than 100K elements in the queue. Your results will vary ...

---

If you don't have faith, simply transfer the contents of your queue into a vector, then show the vector contents in reverse.

And since it is easy, and you want to avoid using a library, simply use an array.

Answer 2

为什么不能简单地反转display（）中的循环，使其从后方开始并向着前方移动？