C语言指针实现简单队列

节点结构体：

typedef struct _node{    int data;    struct _node *next;} Node;

队列结构体：

typedef struct linkedlist{    Node *head;    Node *tail;} Queue;

操作：

//初始化队列void initializeQueue(Queue *queue){    queue->head = NULL;    queue->tail = NULL;}//入队void enQueue(Queue *queue, int data){    Node *node = (Node *) malloc(sizeof(Node));    node->data = data;    if (queue->head == NULL)    {        node->next = NULL;        queue->tail = node;    }    else    {        node->next = queue->head;    }    queue->head = node;}//出队int deQueue(Queue *queue){    Node *tmp = queue->head;    int data;    //1.只有一个元素    //2.多个元素    //   a.遍历到tail上一个tmp    //   b.保存tail的值并free tail所指向的内存    //   c.tail指向tmp    if (queue->head == NULL)    {        data = -1;    }    else if (queue->head == queue->tail)    {        data = tmp->data;        queue->head = queue->tail = NULL;        free(tmp);    }    else    {        while (tmp->next != queue->tail)        {            tmp = tmp->next;        }        data = queue->tail->data;        free(queue->tail);        queue->tail = tmp;        queue->tail->next = NULL;//      queue->tail = tmp;//      tmp = tmp->next;//      queue->tail->next = NULL;//      data = tmp->data;//      free(tmp);    }    return data;}void freeAll(Queue *queue){    while(deQueue(queue) != -1);    printf("\nFree Complete!\n");    return;}void endl(){    printf("\n");}int main(){    Queue queue;    initializeQueue(&queue);    enQueue(&queue, 1);    enQueue(&queue, 2);    enQueue(&queue, 3);    enQueue(&queue, 4);    enQueue(&queue, 5);    printf("%d\n", queue.tail->data);    printf("%d ", deQueue(&queue));    printf("%d ", deQueue(&queue));     //1 2    // queue : 3 4 5    endl();    enQueue(&queue, 10);    enQueue(&queue, 56);    enQueue(&queue, 999);  //queue: 3 4 5 10 56 999    printf("%d ", deQueue(&queue));    printf("%d ", deQueue(&queue));    printf("%d ", deQueue(&queue));    printf("%d ", deQueue(&queue));    printf("%d ", deQueue(&queue));    printf("%d ", deQueue(&queue));    printf("%d ", deQueue(&queue));    freeAll(&queue);    return 0;}

小结：队列实现基于链表，enQueue入队操作基于addHead