链式队列设计。以带头结点的循环单链表实现，并只设尾指针，不设头指针。编写实现这种链式队列的初始化，入队列，出队列，判断非空函数，设计一个主函数，进行测试。用c语言

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

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

typedef struct {
    Node* rear;
} Queue;

// 初始化队列
void initQueue(Queue* q) {
    q->rear = NULL;
}

// 判断队列是否为空
int isEmpty(Queue* q) {
    return q->rear == NULL;
}

// 入队列
void enqueue(Queue* q, int data) {
    Node* newNode = (Node*)malloc(sizeof(Node));
    newNode->data = data;
    if (isEmpty(q)) {
        q->rear = newNode;
        newNode->next = newNode;
    }
    else {
        newNode->next = q->rear->next;
        q->rear->next = newNode;
        q->rear = newNode;
    }
}

// 出队列
int dequeue(Queue* q) {
    if (isEmpty(q)) {
        printf("Queue is empty\n");
        return -1;
    }
    int data = q->rear->next->data;
    Node* temp = q->rear->next;
    if (q->rear == q->rear->next) {
        q->rear = NULL;
    }
    else {
        q->rear->next = temp->next;
    }
    free(temp);
    return data;
}

int main() {
    Queue q;
    initQueue(&q);
    enqueue(&q, 1);
    enqueue(&q, 2);
    enqueue(&q, 3);
    printf("%d\n", dequeue(&q));
    printf("%d\n", dequeue(&q));
    printf("%d\n", dequeue(&q));
    printf("%d\n", dequeue(&q));
    return 0;
}