上文已写队列的顺序存储，本文介绍队列的链式存储

1 队列构造

typedef struct Node{//节点数据
    void *data;
    struct Node *next;
} Node;
typedef struct Queue//队列构造
{
    Node firstNode;
    int size;//队列大小
} Queue;

2 队列初始化

Queue *initQueue()//队列初始化
{
    Queue *queue = (Queue *)malloc(sizeof(Queue));//在堆区申请内存
    if (queue == NULL)
        return NULL; //内存分配失败
    queue->firstNode.data = NULL;//初始化
    queue->firstNode.next = NULL;
    queue->size = 0;
    return queue;
}

3 入队列

int push(void *data, Queue *queue) //入队列，本质是尾插
{
    if (data == NULL || queue == NULL)
        return 0;                 //空指针判断，入队列失败
    Node *node = (Node *)malloc(sizeof(Node));//根据data创建链表节点
    node->data = data;
    node->next = NULL;
    Node *pointer = &queue->firstNode;
    while(pointer->next)//当pointer.next为NULL时跳出循环，即pointer已经指向末位节点
        pointer = pointer->next;
    pointer->next = node;
    queue->size++;                //队列大小+1
    return 1;
}

4 出队列

void *pop(Queue *queue) //出队列，即pop出首个元素
{
    if (queue == NULL || queue->size == 0)
        return NULL;
    Node *popNode = queue->firstNode.next;//首个有效节点即为出队列的节点
    queue->firstNode.next = queue->firstNode.next->next;
    queue->size--;                     //队列大小减1
    return popNode->data;//返回节点的数据域
}

5 队列空与队列大小判断

int isEmptyQueue(Queue *queue)//判断队列是否为空
{
    if (queue == NULL)
        return -1;
    return queue->size == 0; //空时返回1
}
int sizeOfQueue(Queue *queue)//返回队列的大小
{
    if (queue == NULL)
        return -1;
    return queue->size;
}

6函数测试与运行

#include <stdio.h>
#include <stdlib.h>
#include <string.h>
typedef struct Student//以队列存储Student类型数据为例
{
    int id;
    char name[20];
} Student;
int main()
{
    Student stu[6] = {
        {1, "jakes1"},
        {2, "jakes2"},
        {3, "jakes3"},
        {4, "jakes4"},
        {5, "jakes5"},
        {6, "jakes6"},
    };
    Queue *queue = initQueue();//队列初始化
    int pushCount = 0;
    for (int i = 0; i < 6; i++)
    {
        push(&stu[i], queue);//入队列
        printf("第%d次入队列-->id:%d_name:%s\t 队列大小:%d\t队列为空:%d\t\n", ++pushCount, stu[i].id, stu[i].name, sizeOfQueue(queue), isEmptyQueue(queue));
    }
    puts("\n");
    int popCount = 0;
    while (!isEmptyQueue(queue))
    {
        void *popdata = pop(queue);
        Student *stu = (Student *)popdata;//出队列
        printf("第%d次出队列-->id:%d_name:%s\t 队列大小:%d\t队列为空:%d\t\n", ++popCount, stu->id, stu->name, sizeOfQueue(queue), isEmptyQueue(queue));
        free(popdata);
        popdata = NULL;
    }
    return 0;
}

运行结果如下：