数据结构—队列(Queue)

• 队列的定义--Queue

   队列是只允许在表的队尾插入,在表的队头进行删除。队列具有先进先出的特性(FIFO, First In First Out)。

    

• 队列提供了下面的操作

     q.empty()               如果队列为空返回true，否则返回false
     q.size()                返回队列中元素的个数
     q.pop()                 删除队列首元素但不返回其值
     q.front()               返回队首元素的值，但不删除该元素
     q.push()                在队尾压入新元素
     q.back()                返回队列尾元素的值，但不删除该元素

• 队列的实现

     下面是用C++实现的一个队列结构的源码(链表)

         

#pragma once
#include<iostream>
#include<assert.h>
using namespace std; 
template<typename T>
class Queue
{
public:
    Queue()
        :pHead(NULL)
        , pTail(NULL)
    {}
    Queue(const QueueNode<T>& q)
    {
        QueueNode<T>*Node = q.pHead;
        while (Node)
        {
            Push(Node->data);
            Node = Node->next;
        }
    }
    ~Queue()
    {
        QueueNode<T> *Node = pHead;
        while (Node)
        {
            QueueNode<T>*Del = Node;
            Node = Node->next;
            delete Del;
        }
        pHead = NULL;
        size = 0;
    }
    QueueNode<T>& operator = (const QueueNode<T>& q)
    {
        if (this != &q)
        {
           Node<T> *pNode = other._pHead;
            while (NULL != pNode)
            {
                Push(pNode->_data);
                pNode = pNode->_pNext;
            }
        }

        return *this;
    }
    void Push(const T &data)
    {
        if (pHead == NULL)
        {
            pTail = pHead = new QueueNode<T>(data);
        }
        else
        {
            pTail ->next = new QueueNode<T>(data);
            pTail = pTail->next;
        }
    }
    void Pop()
    {
        assert(NULL != pHead);
        if (pHead == pTail)
        {
            delete pHead;
            pHead = pTail = NULL;
        }
        else
        {
            QueueNode<T>*Del = pHead;
            pHead = pHead->next;
            delete Del;
        }
    }
    bool Empty()
    {
        return pHead == NULL;
    }
    T& Fornt()
    {
        assert(pHead);

        return pHead->data;
    }

    T& Back()
    {
        assert(pTail);

        return pTail->data;
    }
    size_t Size()
    {
        while (pHead != NULL)
        {
            size++;
            pHead = pHead->next;
        }
        return size;
    }
    void Print()
    {
        QueueNode<T>*cur = pHead;
        while (cur)
        {
            cout << cur->data << "->";
            cur = cur->next;
        }
        cout << "NULL";
    }
protected:
    QueueNode<T>* _BuyNode(const T& data)
    {
        return new QueueNode<T>(data);
    }
protected:
    QueueNode<T>* pHead;
    QueueNode<T>* pTail;
    size_t size;
};
void main()
{
    Queue<int> q;
    q.Push(6);
    q.Push(6);
    q.Push(9);
    q.Pop();
    q.Print();
    cout<<q.Size();
    cout<<q.Fornt();
    cout << q.Back();
    system("pause");

}