算法复习（6）链表实现的队列

　　使用链表实现的队列，先进先初，压入弹出判空。

// 基于链表的队列
#include <iostream>
using namespace std;
template <typename T>
class Queue
{
public:
    //在构造过程中初始化为空队列
    Queue(void) : m_rear (NULL), m_front (NULL) {}
    //在析构过程中销毁剩余节点
    ~Queue(void)
    {   
        for (Node* next; m_front; m_front = next)
        {   
            next = m_front->m_next;
            delete m_front;
        }   
    }   
    // 压入
    void push(T data)
    {   
        Node* node = new Node(data);
        if (m_rear)
            m_rear->m_next = node;
        else
            m_front = node;
        m_rear = node;
    }
    // 弹出
    T pop(void)
    {
        if (empty())
            throw UnderFlow();
        T data = m_front->m_data;
        Node* next = m_front->m_next;
        delete m_front;
        if (!(m_front = next))
            m_rear = NULL;
        return data;
    }
    // 判空
    bool empty(void)
    {
        return !m_front && !m_rear;
    }
private:
    //下溢异常
    class UnderFlow : public exception
    {
        const char* what(void) const throw ()
        {
            return "队列下溢";
        }
    };
    //节点
    class Node
    {
    public:
        Node(T data, Node* next = NULL) :
            m_data (data), m_next (next) {}
        T m_data;       //数据
        Node* m_next;   //后指针
    };
    Node* m_rear;
    Node* m_front;
};

// 测试基本类型
void test_int(void)
{
        Queue<int> queue;
        for (int i = 0; i < 5; ++i)
            queue.push(i);
        while (!queue.empty())
            cout << queue.pop() << endl;
        cout << endl;
}

// 测试类
struct List
{
    List(string name, int price) : m_name (name),
        m_price (price) {}
    string m_name;
    int m_price;
};
void test_class(void)
{
    List l1("小米", 1999);
    List l2("iphone 5s", 5288);
    Queue<List> queue;
    queue.push(l1);
    queue.push(l2);
//    cout << queue.pop().m_name << queue.pop().m_price << endl;
//    cout << queue.pop().m_price << queue.pop().m_name << endl;
    List l = queue.pop();
    cout << l.m_name << "手机, 价格: " << l.m_price
        << "元." << endl;
}

//测试string类
void test_string(void)
{
    string s1 = "C";
    string s2 = "C++";
    string s3 = "c#";
    string s4 = "java";
    Queue<string> queue;
    queue.push(s1);
    queue.push(s3);
    queue.push(s3);
    queue.push(s4);
    cout << queue.pop() << endl;
    cout << queue.pop() << endl;
    cout << queue.pop() << endl;
    cout << queue.pop() << endl;
    cout << queue.pop() << endl;
}
int main(void)
{
    try
    {
        //test_int();
        //test_string();
        test_class();
    }
    catch (exception& ex)
    {
        cout << ex.what() << endl;
        return -1;
    }
    return 0;
}