C++ STL queue 队列

#include <iostream>
#include <queue>
using namespace std; 
int main()
{
    queue<int> q;
    int choice,e;
    while(true)
    {
        cout<<"1.判断队列是否为空\n"
              "2.队列中元素个数\n"
              "3.删除队首元素\n"
              "4.输出队首元素\n" 
              "5.在队尾插入元素\n"
              "6.输出队尾元素\n";
        cin>>choice;
        switch(choice)
        {
            case 1:cout<<(q.empty()?"空\n":"不空\n");break;
            case 2:cout<<"元素个数为："<<q.size()<<"\n";break;
            case 3:if(q.empty())cout<<"队列为空\n";else{q.pop();cout<<"删除成功\n";}break;
            case 4:q.empty()?cout<<"队列为空\n":cout<<"队首元素为:"<<q.front()<<"\n";break; 
            case 5:cout<<"请输入要插入的元素：";cin>>e;q.push(e);cout<<"插入成功\n";break;
            case 6:q.empty()?cout<<"队列为空\n":cout<<"队尾元素为:"<<q.back()<<"\n";break; 
            default:cout<<"输入错误，请重新输入!\n";
        } 
    }
    return 0;
} 
/************************************************
*                 小柳学渣
*             2019/1/22  20:14
************************************************/