题目来源：严蔚敏《数据结构》C语言版本习题册 3.28

    1. #include<stdio.h>
    2. #include<stdlib.h>
    4. #ifndef BASE
    5. #define BASE
    6. #define TRUE 1
    7. #define FALSE 0
    8. #define OK 1
    9. #define ERROR 0
    10. #define INFEASIBLE -1
    11. #define OVERFLOW -2
    12. typedef int Status;
    13. typedef int bool;
    14. #endif
    16. // 实现：队列
    17. // 数据结构：循环链表（带头结点）
    18. // 结构体：只设置一个指针指向队尾元素结点（不设头指针）
    20. typedef int ElemType;
    21. typedef struct NodeType{
    22.     ElemType data;
    23.     struct NodeType *next;
    24. }QNode, *QPtr;
    25. typedef struct{
    26.     QPtr rear;
    27. }Queue;
    29. Status InitQueue(Queue *pQ) {
    30.     QNode *newNode;
    31.     //头结点
    32.     newNode = (QNode *)malloc(sizeof(QNode));
    33.     if (!newNode) exit(OVERFLOW);
    34.     newNode->next = newNode; //指向自己，循环链表
    35.     pQ->rear = newNode; //尾指针指向头结点
    36.     return OK;
    37. }
    39. Status EnQueue(Queue *pQ, ElemType e) {
    40.     QNode *newNode;
    41.     newNode = (QNode *)malloc(sizeof(QNode));
    42.     if (!newNode) exit(OVERFLOW);
    43.     newNode->data = e;
    44.     newNode->next = pQ->rear->next;
    45.     pQ->rear->next = newNode;
    46.     pQ->rear = newNode;
    47.     return OK;
    48. }
    50. Status DeQueue(Queue *pQ,ElemType *e) {
    51.     QNode *tmp, *top;
    53.     if (pQ->rear->next==pQ->rear) return ERROR; //空
    54.     top = pQ->rear->next; //头结点
    55.     tmp = top->next; //得到队列的第一个元素
    56.     *e = tmp->data; //赋值
    57.     //删除队列的第一个元素
    58.     top->next = tmp->next;
    59.     free(tmp);
    60.     //如果队列又为空，则需要改变尾指针的指向
    61.     if (top->next==top) pQ->rear=top;
    62.     return OK;
    63. }
    65. Status Debug(Queue Q, void (*Visit)(ElemType e)) {
    66.     QNode *top,*tmp;
    67.     printf("----------------\n");
    68.     printf("rear指向：%d\n", Q.rear->data); //debug
    69.     top = Q.rear->next;
    70.     tmp = top;
    71.     do {
    72.         Visit(tmp->data);
    73.         tmp=tmp->next;
    74.     }while(tmp!=top);
    75.     printf("\n----------------\n");
    76.     return OK;
    77. }
    79. void visit(ElemType e) {
    80.     printf("%d\t", e);
    81. }
    83. int main() {
    84.     int c;
    85.     int tmp;
    86.     Queue Q;
    87.     InitQueue(&Q);
    88.     Debug(Q, &visit);
    89.     while (1) {
    90.         scanf("%d", &c);
    91.         switch(c) {
    92.         case 1:scanf("%d",&tmp);EnQueue(&Q, tmp);Debug(Q,&visit);break;
    93.         case 2:DeQueue(&Q, &tmp);printf("抛出%d\n", tmp);Debug(Q,&visit);break;
    94.         }
    95.     }
    96.     return 0;
    97. }