《大话数据结构》读书笔记之链式队列和源码

/************************************链队列的主要知识点**************************************
链队列其实是线性表的单链表，只不过只能尾进头出。

队头指针front指向链表的头结点，队尾指针rear指向链表的终端结点。

空队列是，队尾指针和队头指针都指向头结点。
***********************************************************************************************/


#include "declear.h"
#include <stdio.h>
#include <stdlib.h>
#include "math.h"  

typedef struct QNode
{
	QElemType data;
	struct QNode *next;
}QNode, *QueuePtr;

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

Status InitQueue(LinkQueue *Q)
{
	Q->front = Q->rear = (QueuePtr)malloc(sizeof(QNode));
	if(!Q->front)
	{
		exit(OVERFLOW);
	}
	Q->rear = NULL;

	return OK;
}

int LengthQue(LinkQueue Q)
{
	int len = 0;
	QueuePtr tem;

	tem = Q.front;

	while(tem != Q.rear)
	{
		tem = tem->next;
		++len;
	}

	return len;
}


Status DestroyQue(LinkQueue *Q)
{
	QueuePtr tem;
	
	while (Q->front)
	{
		tem = Q->front;
		Q->front = Q->front->next;
		free(tem);
	}

	return OK;
}
Status ClearQueue(LinkQueue *Q)
{
	QueuePtr tem;
	tem = Q->front->next;
	
	while (!(Q->front->next))
	{
		tem = Q->front->next;
		Q->front->next = Q->front->next->next;
		free(tem); 
	}
	Q->rear = Q->front;
	Q->front->next = NULL;
	
	return OK;
}
Status InsertQueue(LinkQueue *Q, QElemType elem)
{
	QueuePtr tem;
	tem = (QueuePtr)malloc(sizeof (QNode));
	
	if(!tem)					//分配内存失败退出。
	{
		exit(OVERFLOW);
	}

	tem->data = elem;
	tem->next = NULL;
	Q->rear->next = tem;		//在尾部插入元素
	Q->rear = Q->rear->next;	//更新尾部指针

	return OK;
}

Status DeleteQueue(LinkQueue *Q)
{
	QueuePtr p;

	if(Q->rear == Q->front)
	{
		return ERROR;
	}
	
	p = Q->front->next;
	Q->front->next = p->next;	//修改front指向，使其指示Q->front->next->next

	if (p->next == Q->rear)		//如果*Q只有一个结点，即Q->front->next == Q->rear，则给Q->rear赋值
	{
		Q->rear = Q->front;
	}

	free(p);
	return OK;
}


int main ()
{
	LinkQueue linkQue;
	Status s;

	s = InitQueue (&linkQue);

	if(s)
	{
		printf("成功地构造了一个空队列!\n");
		printf("是否成功清除队列？%d(1:是 0:否)  \n",ClearQueue(&linkQue));
		printf("队列的长度为%d\n",LengthQue(linkQue));

		InsertQueue(&linkQue, 22);
		InsertQueue(&linkQue, 3);
		InsertQueue(&linkQue, 3);
		InsertQueue(&linkQue, 3);
		InsertQueue(&linkQue, 3);
		DeleteQueue(&linkQue);

		printf("队列的长度为%d\n",LengthQue(linkQue));

	}




	return 0;
}