push完之后再添加

void myfun()
{
    queue<int>q;
    q.push(1);
    q.push(2);
    q.push(3);

    int size=q.size();
    for(int i=0;i<size;i++)
    {
        cout<<q.front()<<endl;
        q.push(q.front());
        q.pop();
    }
    cout<<"------------"<<endl;
    while(q.size())
    {
        cout<<q.front()<<endl;
        q.pop();
    }

}