c++ 两个栈实现队列

#include <cstdlib>
#include <iostream>
#include <stack>
/*两个栈实现队列*/
using namespace std;
template<class T>
struct MyQueue
{
       void push(T &t)
       {
            s1.push(t);
       }
       T front()
       {
                if(s2.empty())
                {
                              if(s1.size()==0) throw;
                              while(!s1.empty())
                              {
                                                s2.push(s1.top());
                                                s1.pop();
                              }
                }
                return s2.top();
       }
       void pop()
       {
            if(s2.empty())
            {
                          while(!s1.empty())
                          {
                                            s2.push(s1.top());
                                            s1.pop();
                          }
            }
            if(!s2.empty())
            s2.pop();
       }
       stack<T> s1;
       stack<T> s2;
};
int main(int argc, char *argv[])
{
    MyQueue<int> mq;
    int i;
    for(i=0;i<10;++i)
    {
                     mq.push(i);
    }
    for(i=0;i<10;++i)
    {
                     cout<<mq.front()<<endl;
                     mq.pop();
    }
    system("PAUSE");
    return EXIT_SUCCESS;
}