数据结构之队列

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一、队列的介绍

队列（Queue），是一种线性存储结构。它有以下几个特点：

1、队列中数据是按照”先进先出（FIFO, First-In-First-Out）”方式进出队列的。
2、队列只允许在”队首”进行删除操作，而在”队尾”进行插入操作。队列通常包括的两种操作：入队列和出队列。

1. 队列的示意图

这里写图片描述

队列中有10，20，30共3个数据。

2. 出队列

这里写图片描述

出队列前：队首是10，队尾是30。
出队列后：出队列(队首)之后。队首是20，队尾是30。

3. 入队列

这里写图片描述

入队列前：队首是20，队尾是30。
入队列后：40入队列(队尾)之后。队首是20，队尾是40。

二、队列的实现

实现1：数组实现
实现2：链表实现

数组实现完整代码：

    //头文件#ifndef QUEUE_H#define QUEUE_Hclass Queue{public:    Queue();    ~Queue();    void EnQueue(int x);    int DeQueue();    int GetSize(){  return (tail + MAXSIZE - head) % MAXSIZE; }    int GetHead();    int GetTail();    bool Empty(){ return (head == tail) ? 1 : 0; }    bool Full(){ return (head == tail + 1) ? 1 : 0; }    void Display();private:    int *Data;    const int MAXSIZE=50;    int head;    int tail;};#endif // !QUEUE_H//实现文件#include "queue.h"#include <iostream>Queue::Queue(){    Data = new int[MAXSIZE];    head = 1;    tail = 1;}Queue::~Queue(){    while (!Empty())        DeQueue();    delete []Data;}void Queue::EnQueue(int x){    if (Full())        std::cout << "队列已满！" << std::endl;    else    {        if (tail == MAXSIZE)        {            tail = 1;            Data[tail] = x;        }        else            Data[tail++] = x;    }}int Queue::DeQueue(){    if (Empty())        std::cout << "队列已空！" << std::endl;    else    {        int x = Data[head];         if (head == MAXSIZE)            head = 1;        else            head++;        return x;    }}int Queue::GetHead(){    if (Empty())        std::cout << "队列已空！" << std::endl;    else        return Data[head];}int Queue::GetTail(){    if (Empty())        std::cout << "队列已空！" << std::endl;    else        return Data[tail - 1];}void Queue::Display(){    if (Empty())        std::cout << "队列已空！" << std::endl;    else    {        int hd = head;        while (hd != tail)        {            if (hd == MAXSIZE)                hd = 1;            std::cout << Data[hd++] << " ";        }    }}//测试文件#include <iostream>#include "queue.h"using namespace std;int main(){    Queue queue;    cout << "队列中元素数目：";    cout << queue.GetSize() << endl;    for (int i = 0; i < 30; ++i)        queue.EnQueue(i);    cout << "队列中元素数目：";    cout << queue.GetSize() << endl;    for (int i = 0; i < 5; ++i)    cout << "删除元素：" << queue.DeQueue() << endl;    cout << "队列头元素：";    cout << queue.GetHead() << endl;    cout << "队列尾元素：";    cout << queue.GetTail()<< endl;    cout << "队列中元素数目：";    cout << queue.GetSize() << endl;    for (int i = 0; i < 22; ++i)        queue.EnQueue(i);    cout << "队列中元素：";    queue.Display();    cout << endl;    cout << "队列头元素：";    cout << queue.GetHead() << endl;    cout << "队列尾元素：";    cout << queue.GetTail() << endl;    cout << "队列中元素数目：";    cout << queue.GetSize() << endl;    system("pause");    return 0;}

链表实现完整代码：

//头文件#ifndef LINKQUEUE_H#define LINKQUEUE_H#include <iostream>struct Node{    int data;    Node *next;};class LinkQueue{public:    LinkQueue();    ~LinkQueue();    void EnQueue(int x);    int DeQueue();    void Display();    bool Empty(){ return (tail == head) ? 1 : 0; }private:    Node *head; //head指向无用的头结点, head->pNext才是指向队首元素， tail指向队尾元素    Node *tail;};#endif // !LINKQUEUE_H//实现文件#include "linkqueue.h"LinkQueue::LinkQueue(){    head = tail = new Node;    tail->next = NULL;}LinkQueue::~LinkQueue(){    while (Empty())        DeQueue();    delete head;}void LinkQueue::EnQueue(int x){    Node *n = new Node;    n->data = x;    n->next = NULL;    tail->next = n; //将n挂到队列尾部     tail = n; //为指针后移}int LinkQueue::DeQueue(){    if (Empty())        std::cout << "队列为空！" << std::endl;    else    {        Node *temp = head->next;        head->next = temp->next;        int x = temp->data;        delete temp;        if (head->next == NULL)            tail = head;        return x;    }}void LinkQueue::Display(){    if (Empty())        std::cout << "队列为空！" << std::endl;    else    {        Node *node = head->next;        std::cout << "队列中的元素是：";        while (node != tail->next)        {            std::cout << node->data << " ";            node = node->next;        }        delete node;    }}//测试文件#include "linkqueue.h"using namespace std;int main(){    LinkQueue lq;    for (int i = 0; i < 20; ++i)        lq.EnQueue(i);    lq.Display();    cout << endl;    for (int i = 0; i < 5; ++i)        lq.DeQueue();    lq.Display();    cout << endl;    system("pause");    return 0;}

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