使用两个队列实现栈

代码：

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

template<class T>
class Cstack
{
public:
    Cstack();
    ~Cstack();
    void push(const T &element);
    T pop();
    unsigned length();

private:
    queue<T> queue1;
    queue<T> queue2;
};

template<class T>
Cstack<T>::Cstack(){}

template<class T>
Cstack<T>::~Cstack(){}

template<class T>
void Cstack<T>::push(const T &element)
{
    queue1.push(element);
}

template<class T>
T Cstack<T>::pop()
{
    if (queue1.size() > 0 || queue2.size() > 0)
    {
        if (queue2.size() <= 0)
        {
            while (queue1.size()>1)
            {
                T &data = queue1.front();
                queue1.pop();
                queue2.push(data);
            }
            T res = queue1.front();
            queue1.pop();
            return res;
        }
        else
        {
            while (queue2.size()>1)
            {
                T &data = queue2.front();
                queue2.pop();
                queue1.push(data);
            }
            T res = queue2.front();
            queue2.pop();
            return res;
        }
    }
    else
    {
        throw exception("stack is empty!");
    }
}

template<class T>
unsigned Cstack<T>::length()
{
    return queue1.size() > queue2.size() ? queue1.size() : queue2.size();
}

int main()
{
    int a[] = { 1, 2, 3, 4, 5, 6 };
    Cstack<int> mystack;
    for (int i = 0; i < 6; i++){ mystack.push(a[i]); }
    while (mystack.length()>0)
    {
        cout << mystack.pop() << "  ";
    }
    cout << endl;
    return 0;
}