双栈模拟队列

#include <iostream>
#include <stack>
using namespace std;

class QueuebyStack
{
public:
    void enqueue(char ch)
    {
        s1.push(ch);
    }
    void dequeue()
    {
        if(s2.empty())
        {
            while(!s1.empty())
            {
                char temp = s1.top();
                s2.push(temp);
                s1.pop();
            }
        }
        s2.pop();
    }
    bool empty()
    {
        return s1.empty()&&s2.empty();
    }
    char front()
    {
        if(s2.empty())
        {
            while(!s1.empty())
            {
                char temp = s1.top();
                s2.push(temp);
                s1.pop();
            }
        }
        return s2.top();
    }
    long size() const
    {
        return s1.size()+s2.size();
    }
private:
    stack<char> s1;
    stack<char> s2;
};

int main()
{
    QueuebyStack q;
    char ch;
    while(cin>>ch&&ch != '0')
    {
        q.enqueue(ch);
    }
    while(!q.empty())
    {
        cout<<q.front()<<" ";
        q.dequeue();
    }
    cout<<endl;
    return 0;
}