以带头结点的循环链表表示队列，并且只设一个指针指向队尾元素。

出队的时候一定要注意是不是最后一个元素出队。

//假设以带头结点的循环链表表示队列，并且只设一个指针指向队尾元素结点，试编写相
//应的初始化、入队以及出队算法。
#include<stdio.h>
#include<stdlib.h>
typedef enum { ERROR, OK, EMPTY, NOTEMPTY } bool;
typedef int Status;
typedef int ElemType;
typedef struct Node {
	ElemType data;
	struct Node *next;

}Queue, *LinkQueue;
LinkQueue Rear;
bool InitQueue(LinkQueue Q) {
	Q->next = Q;
	Rear = Q;
	return OK;
}

bool JudgeQueue(LinkQueue Q) {
	if (Rear == Q) {
		printf("Queue is Empty\n");
		return EMPTY;
	}
	printf("Queue is not empty\n");
	return NOTEMPTY;
}

bool EnQueue(LinkQueue Q, ElemType e) {
	LinkQueue p;
	p = (LinkQueue)malloc(sizeof(Queue));
	if (p == NULL)
		return ERROR;
	p->data = e;
	p->next = Rear->next;
	Rear->next = p;
	Rear = p;
	return OK;
}

bool DeQueue(LinkQueue Q, ElemType *e) {
	if (Rear == Q) {
		printf("Queue is Empty\n");
		return ERROR;
	}
	LinkQueue p;
	p = Rear->next->next;
	*e = p->data;
	Rear->next->next = p->next;
	if (Rear == p)
		Rear = Q;
	free(p);
	return OK;
}
//测试
int main() {
	LinkQueue Q = NULL;
	Q = (LinkQueue)malloc(sizeof(Queue));
	bool flag;
	flag = InitQueue(Q);
	if (flag == ERROR)
		printf("Init RROR\n");
	else if (flag == OK)
		printf("Init OK\n");

	JudgeQueue(Q);
	ElemType e;
	for (int i = 0; i < 4; i++) {
		printf("请输入：\n");
		scanf_s("%d", &e);
		flag = EnQueue(Q, e);
		if (flag == OK)
			printf("Enter OK\n");
		else
			printf("Enter ERROR\n");
	}
	JudgeQueue(Q);
	for (int i = 0; i < 3; i++) {
		flag = DeQueue(Q, &e);
		if (flag == ERROR) {
			printf("Queue is EmPty\n");
			continue;
		}
		if (flag == OK) {
			printf("%d\n", e);
		}
		JudgeQueue(Q);
	}
	for (int i = 0; i < 4; i++) {
		printf("请输入：\n");
		scanf_s("%d", &e);
		flag = EnQueue(Q, e);
		if (flag == OK)
			printf("Enter OK\n");
		else
			printf("Enter ERROR\n");
	}
	JudgeQueue(Q);
	for (int i = 0; i < 5; i++) {
		flag = DeQueue(Q, &e);
		if (flag == ERROR) {
			printf("Queue is EmPty\n");
			continue;
		}
		if (flag == OK) {
			printf("%d\n", e);
		}
		JudgeQueue(Q);
	}
}

这个写的很好