#include <iostream>

using namespace std;

const int N = 100010;

struct Node {
    int  val;
    Node *next;
    Node (): next(NULL){}
    Node(int _val): val(_val), next(NULL){}
};

void print(Node *front)
{
    for(auto p = front; p->val; p = p->next)
    {
        cout << p->val << " ";
    }cout << endl;
}

int main()
{
    Node *front = new Node(), *rear = front;

    rear->val = 1;
    rear->next = new Node();
    rear = rear->next;
    if(front != rear )
    {
        cout << "队列不为空" << endl;
        print(front);
        cout << "对头是" << front->val << endl;
    }else
        cout << "队列为空" << endl;

    rear->val = 2;
    rear->next = new Node();
    rear = rear->next;
    if(front != rear )
    {
        cout << "队列不为空" << endl;
        print(front);
        cout << "对头是" << front->val << endl;
    }else
        cout << "队列为空" << endl;

    rear->val = 3;
    rear->next = new Node();
    rear = rear->next;
    if(front != rear )
    {
        cout << "队列不为空" << endl;
        print(front);
        cout << "对头是" << front->val << endl;
    }else
        cout << "队列为空" << endl;

    auto a = front;
    front = front->next;
    delete a;
    if(front != rear )
    {
        cout << "队列不为空" << endl;
        print(front);
        cout << "对头是" << front->val << endl;
    }else
        cout << "队列为空" << endl;

    auto b = front;
    front = front->next;
    delete b;
    if(front != rear )
    {
        cout << "队列不为空" << endl;
        print(front);
        cout << "对头是" << front->val << endl;
    }else
        cout << "队列为空" << endl;

    auto c = front;
    front = front->next;
    delete c;
    if(front != rear )
    {
        cout << "队列不为空" << endl;
        print(front);
        cout << "对头是" << front->val << endl;
    }else
        cout << "队列为空" << endl;
    return 0;
}