LinkQueue——链式队列

链式队列实现起来很简单。

唯一需要注意的是：

在入队和出队时，需要分别处理一下队头和队尾为空的情况。

/*
** File name: LinkQueue.h
** Author: ZhouFeng
** Date: 2012/03/28
*/
#ifndef LINK_QUEUE_H
#define LINK_QUEUE_H

#define BOOL int
#define FALSE 0
#define TRUE 1
#define ERROR 0
#define SUCCESS 1

typedef int EleType;
typedef struct LQNode
{
    EleType data;
    struct LQNode *pNext;
}LQNode;
typedef struct LinkQueue
{
    LQNode *pFront;
    LQNode *pRear;
}LinkQueue;

void InitLinkQueue(LinkQueue *LQ);
BOOL IsLinkQueueEmpty(LinkQueue *LQ);
int LinkQueueAppend(LinkQueue *LQ, EleType data);
int LinkQueueDelete(LinkQueue *LQ, EleType *pData);
int GetQueue(LinkQueue *LQ, EleType *pData);
void FreeQueue(LinkQueue *LQ);

#endif

/*
** File name: LinkQueue.c
** Author: ZhouFeng
** Date: 2012/03/28
*/
#include <stdlib.h>
#include <stddef.h>
#include "LinkQueue.h"

void InitLinkQueue(LinkQueue *LQ)
{
    if(LQ == NULL)
    {
	return;
    }

    LQ->pFront = NULL;
    LQ->pRear = NULL;
}

BOOL IsLinkQueueEmpty(LinkQueue *LQ)
{
    if(LQ == NULL)
    {
	return TRUE;
    }

    if(LQ->pFront == NULL)
    {
	return TRUE;
    }
    else
    {
	return FALSE;
    }
}

int LinkQueueAppend(LinkQueue *LQ, EleType data)
{
    LQNode *pNewNode;
    
    if(LQ == NULL)
    {
	return ERROR;
    }

    pNewNode = (LQNode*)malloc(sizeof(LQNode));
    pNewNode->data = data;
    pNewNode->pNext = NULL;
    
    if(LQ->pRear != NULL)
    {
	LQ->pRear->pNext = pNewNode;
    }
    LQ->pRear = pNewNode;

    if(LQ->pFront == NULL)
    {
	LQ->pFront = pNewNode;
    }

    return SUCCESS;
}

int LinkQueueDelete(LinkQueue *LQ, EleType *data)
{
    LQNode *pDel;
    
    if(LQ == NULL || data == NULL)
    {
	return ERROR;
    }

    if(LQ->pFront == NULL)
    {
	return ERROR;
    }

    *data = LQ->pFront->data;
    pDel = LQ->pFront;
    LQ->pFront = LQ->pFront->pNext;

    if(LQ->pFront == NULL)
    {
	LQ->pRear = NULL;
    }
    free(pDel);

    return SUCCESS;
}

int GetQueue(LinkQueue *LQ, EleType *pData)
{
    if(LQ == NULL || LQ->pFront == NULL || pData == NULL)
    {
	return ERROR;
    }

    *pData = LQ->pFront->data;

    return SUCCESS;
}

void FreeQueue(LinkQueue *LQ)
{
    LQNode *pDel;
    
    if(LQ == NULL)
    {
	return;
    }

    while(LQ->pFront != NULL)
    {
	pDel = LQ->pFront;
	LQ->pFront = LQ->pFront->pNext;
	free(pDel);
    }

    LQ->pRear = LQ->pFront = NULL;
}