用两个栈模拟队列

　　用两个栈模拟队列，算法如下图所示：

程序如下：

Queue类的接口与实现

/********************************************************************
    created:    2013/08/18
    created:    18:8:2013   21:54
    file base:    Queue
    file ext:    h
    author:        Justme0 (http://blog.csdn.net/Justme0)
    
    purpose:    用两个栈模拟队列
*********************************************************************/

#ifndef _QUEUE_H_
#define _QUEUE_H_

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

template <class T>
class Queue {
public:
    bool empty() const;
    void push(T x);
    T pop();

protected:
    stack<T> _s_push;
    stack<T> _s_pop;
};

template <class T>
bool Queue<T>::empty() const {
    return this->_s_pop.empty() && this->_s_push.empty();
}

template <class T>
void Queue<T>::push(T x) {
    _s_push.push(x);
}

template <class T>
T Queue<T>::pop() {
    assert(!empty());

    if (this->_s_pop.empty()) {
        while (!_s_push.empty()) {
            _s_pop.push(_s_push.top());
            _s_push.pop();
        }
    }

    T top = _s_pop.top();
    _s_pop.pop();
    return top;
}

#endif

测试程序

/********************************************************************
    created:    2013/08/18
    created:    18:8:2013   21:53
    file base:    main
    file ext:    cpp
    author:        Justme0 (http://blog.csdn.net/Justme0)
    
    purpose:    测试程序
*********************************************************************/

#include "Queue.h"
#include <iostream>

using namespace std;

int main(int argc, char **argv) {
    Queue<int> obj;

    for (int i = 0; i < 10; ++i) {
        obj.push(i);
    }

    for (int i = 0; i < 5; ++i) {
        cout << obj.pop() << endl;
    }

    for (int i = 10; i < 20; ++i) {
        obj.push(i);
    }

    while (!obj.empty()) {
        cout << obj.pop() << endl;
    }

    return 0;
}

运行结果

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请按任意键继续. . .