个人笔记--（单链表）队列的初始化，入队和出队

队列的一些基本操作

初始化队列

Status InitQueue(LinkQueue &q)
{
    q.front=q.rear=(QueuePtr)malloc(sizeof(QNode));//申请空间
    if(!q.front)//内存不够，申请失败
        exit(OVERFLOW);
    q.front->next=NULL;//队头指针指向空
    return OK;
}

销毁队列

Status DestroyQueue(LinkQueue &q){
    while(q.front){
        q.rear=q.front->next;
        free(q.front);
        q.front=q.rear;
    }
    return OK;
}

清空队列

Status ClearQueue(LinkQueue &q)
{
	QueuePtr p1,p2;
	q.rear=q.front;
	p1=q.front->next;
	q.front->next=NULL;
	while(p1)
	{
		p2=p1;
		p1=p1->next;
		free(p2);	
	}
	return OK;
}

队列判空

Status EmptyQueue(LinkQueue &q)
{
	if(q.front->next==NULL)
		return 1;
	else
		return 0;
}

求队列长度

Status LengthQueue(LinkQueue &q)
{
	int len=0;
	QueuePtr p=q.front;
	while(q.rear!=p)
	{
		len++;
		p=p->next;
	}
	return len;
}

取队头元素

Status GetHead(LinkQueue Q,QElemType &e)
{
		QueuePtr p;
		if(q.front==q.rear)//队列为空，退出
			return ERROR;
		p=q.front->next;
		e=p->data;
		return OK;
}

入队

Status InsertQueue(LinkQueue &q,QElemType e){
    QueuePtr p;
    p=(QueuePtr)malloc(sizeof(QNode));
    if(!p)
        exit(OVERFLOW);
    p->data=e;
    p->next=NULL;
    q.rear->next=p;//插入队尾
    q.rear=p;//更新队尾
    return OK;
}

出队

Status DeleteQueue(LinkQueue &q,QElemType &e){
    QueuePtr p;
    if(q.front==q.rear)
        return ERROR;//队列为空了
    p=q.front->next;//取队头元素位置
    e=p->data;//取队头值
    q.front->next=p->next;//更新队头元素
    if(q.rear==p)//出队是队尾元素情况
        q.rear=q.front;
    free(p);//释放p
    return OK;
}

输出队列

Status ShowQueue(LinkQueue &q)
{
	QueuePtr p=q.front->next;
	while(p)
	{
		cout<<p->data<<' ';
		p=p->next;
	}
	cout<<endl;
	return OK;
}

完整代码

#include<bits/stdc++.h>
using namespace std;
#define OK 1
#define ERROR 0
#define Listsize 100
typedef int Status;
typedef int QElemType;
typedef struct QNode{
	QElemType      data;
	struct QNode  *next;
}QNode, *QueuePtr;

typedef struct{
	QueuePtr front;
	QueuePtr rear;
}LinkQueue;

int init=0,des=0;
LinkQueue q;

Status InitQueue(LinkQueue &q)
{
    q.front=q.rear=(QueuePtr)malloc(sizeof(QNode));
    if(!q.front )
        exit(OVERFLOW);
    q.front->next=NULL;
    return OK;
}

Status DestroyQueue(LinkQueue &q){
    while(q.front){
        q.rear=q.front->next;
        free(q.front);
        q.front=q.rear;
    }
    return OK;
}

Status ClearQueue(LinkQueue &q)
{
	QueuePtr p1,p2;
	q.rear=q.front;
	p1=q.front->next;
	q.front->next=NULL;
	while(p1)
	{
		p2=p1;
		p1=p1->next;
		free(p2);	
	}
	return OK;
}

Status InsertQueue(LinkQueue &q,QElemType e){
    QueuePtr p;
    p=(QueuePtr)malloc(sizeof(QNode));
    if(!p)
        exit(OVERFLOW);
    p->data=e;
    p->next=NULL;
    q.rear->next=p;
    q.rear=p;
    return OK;
}

Status DeleteQueue(LinkQueue &q,QElemType &e){
    QueuePtr p;
    if(q.front==q.rear)
        return ERROR;
    p=q.front->next;
    e=p->data;
    q.front->next=p->next;
    if(q.rear==p)
        q.rear=q.front;
    free(p);
    return OK;
}

Status EmptyQueue(LinkQueue &q)
{
	if(q.front->next==NULL)
		return 1;
	else
		return 0;
}

Status LengthQueue(LinkQueue &q)
{
	int len=0;
	QueuePtr p=q.front;
	while(q.rear!=p)
	{
		len++;
		p=p->next;
	}
	return len;
}

Status GetHead(LinkQueue Q,QElemType &e)
{
		QueuePtr p;
		if(q.front==q.rear)
			return ERROR;
		p=q.front->next;
		e=p->data;
		return OK;
}

Status ShowQueue(LinkQueue &q)
{
	QueuePtr p=q.front->next;
	while(p)
	{
		cout<<p->data<<' ';
		p=p->next;
	}
	cout<<endl;
	return OK;
}

int main()
{
	int order,len,e;
	cout<<"*--------------队列--------------*"<<endl;
	cout<<"*---------1.初始化队列-----------*"<<endl;
	cout<<"*---------2.销毁队列-------------*"<<endl;
	cout<<"*---------3.清空队列-------------*"<<endl;
	cout<<"*---------4.队列判空-------------*"<<endl;
	cout<<"*---------5.求队列长度-----------*"<<endl;
	cout<<"*---------6.获取队头元素---------*"<<endl;
	cout<<"*---------7.入队-----------------*"<<endl;
	cout<<"*---------8.出队-----------------*"<<endl;
	cout<<"*---------9.输出所有元素---------*"<<endl;
	do{
	cout<<"请输入指令"<<endl;
	cin>>order;
	if(order==0 || order>9)
		cout<<"没有该指令"<<endl;
	else if(!init && order>1)
		cout<<"请先初始化队列"<<endl;
	else if(des && order>1)
		cout<<"队列已销毁，请先初始化"<<endl;
	else
		switch(order)
		{
			case 1:
				InitQueue(q);
				init=1;
				des=0;
				cout<<"初始化队列完成"<<endl;
				break;
			case 2:
				DestroyQueue(q);
				des=1;
				cout<<"队列已销毁"<<endl;
				break;
			case 3:
				ClearQueue(q);
				cout<<"队列已清空"<<endl;
				break;
			case 4:
				if(!EmptyQueue(q))
					cout<<"队列非空"<<endl;
				else
					cout<<"队列为空"<<endl;
				break;
			case 5:
				len=LengthQueue(q);
				cout<<"队列长度为："<<len<<endl;
				break;
			case 6:
				if(!GetHead(q,e))
					cout<<"队列为空"<<endl; 
				else
					cout<<"队头元素为"<<e<<endl; 
				break;
			case 7:
				cout<<"请输入插入元素：";
				cin>>e;
				InsertQueue(q,e);
				cout<<"入队成功"<<endl;
				break;
			case 8:
				if(DeleteQueue(q,e))
					cout<<"出队成功"<<endl;
				else
					cout<<"队列为空"<<endl;
				break;
			case 9:
				cout<<"队列为："<<endl;
				ShowQueue(q);
				break;
			default:
				cout<<"程序已退出"<<endl;
				break;
		}
	}while(order>=0);
	return 0;	 
}

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