数据结构--队列--链式存储

队列一般叫优先级队列.这是跟它的相关应用有关的.

#include <stdio.h>
#include <stdlib.h> 

typedef int elemType;

struct sNode{               /*队列节点*/
    elemType data;
    struct sNode *next;
};

struct queueLK{
    struct sNode *front;    /*队列头指针*/ 
    struct sNode *rear;     /*队列尾指针*/
};

/* 1.初始化链队*/
void initQueue(struct queueLK *hq)
{
    hq->front = hq->rear = NULL;
    return;    
}
 
/* 2.向链队中插入一个元素*/
void enQueue(struct queueLK *hq, elemType x)
{
    struct sNode *newP;
    newP = malloc(sizeof(struct sNode));
    if(newP == NULL)
    {
        printf("空间申请失败!\n");
        system("pause");
    }
    newP->data = x;
    newP->next = NULL; 
    if(hq->rear == NULL)
    {
        hq->front = hq->rear = newP;    
    }else{
        hq->rear->next = newP;
        hq->rear = newP;    
    } 
    return; 
            
} 

/* 3.从队列中删除一个元素*/
elemType outQueue(struct queueLK *hq)
{
    if(hq->front == NULL)
    {
        printf("队列为空...\n"); 
        return -1;    
    }
    struct sNode *temp = hq->front;
    elemType data = temp->data;
     
    if(hq->front == hq->rear)       /*若只有一个节点*/ 
    { 
        hq->front = hq->rear = NULL;
    }else{
        hq->front=hq->front->next;    
    } 
    free(temp);
    
    return data; 
} 

/* 4.读取队首元素*/
elemType peekQueue(struct queueLK *hq)
{
    if(hq->front == NULL)
    {
        printf("队列为空,读取失败.\n");
        return -1;    
    }    
    return hq->front->data; 
} 
/* 5.检查链队是否为空,若为空返回1,否则返回0*/
int emptyQueue(struct queueLK *hq)
{
    if(hq->front == NULL)
    {
        return 1;    
    }else{
        return 0;
    } 
} 
/* 6.清楚队列中的所有元素*/
void clearQueue(struct queueLK *hq)
{
    if(hq->front == NULL)
    {
        return;    
    }
    struct sNode *temp = hq->front;
    while(hq->front != NULL)
    {
        hq->front = hq->front->next;
        free(temp);
        temp = hq->front;    
    }
    hq->rear = NULL;         
} 
 
#if 1
int main()
{
    struct queueLK hq; 
    int a[] = {2,4,5};
    int i; 
    
    initQueue(&hq); 
    for(i = 0;i<sizeof(a)/4;i++)
    {
        enQueue(&hq,a[i]);       
    }
    if(emptyQueue(&hq))
    {
        printf("队列为空...\n");    
    }
    printf("队列头为:%d\n",peekQueue(&hq));
    printf("出队列:%d\n",outQueue(&hq)); 
    printf("出队列:%d\n",outQueue(&hq));
    printf("出队列:%d\n",outQueue(&hq));
    
    printf("入队列...\n");
    enQueue(&hq,7);
    printf("队列头为:%d\n",peekQueue(&hq));
    
    clearQueue(&hq);
    printf("清空队列.\n"); 
    
    if(emptyQueue(&hq))
    {
        printf("队列为空...\n");    
    }
    system("pause");
    return 0;    
} 
#endif 

************************************************************************

运行结果

************************************************************************

队列头为:2
出队列:2
出队列:4
出队列:5
入队列...
队列头为:7
清空队列.
队列为空...
请按任意键继续. . .