//创建 循环链表

Student * CreateCircleLink_Table(void){

    int i = ;

    Student *head = NULL;

    head = (Student *)malloc(sizeof(Student));

    head->name[]='\0';

    head->point = ;

    head->stu = NULL;

    //循环节点

    Student *circleStu = NULL;

    Student *temp = NULL;

    Student *currentNode = head;

    while (i<=) {

        temp = (Student *)malloc(sizeof(Student));

        strncpy(temp->name,"Node",sizeof(temp->name));

        temp->point = i;

        temp->stu = NULL;

        currentNode->stu = temp;

        currentNode = temp;

        //循环节点

        if (i==) {

            circleStu = currentNode;

        }

        i++;

    }

    //最后 合并循环节点

    currentNode->stu = circleStu;

    return head;

}

//已知循环节点 查询 主要为了验证循环链表是否可用

void SelectCircleLinkTable(Student *student){

    Student *next = student->stu;

    int i = ;

    Student *circleStu = NULL;

    while (next) {

        if (circleStu!=NULL&&next->point == circleStu->point) {

            printf("循环节点%d,结束循环\n",next->point);

            break;

        }

        if (i==) {

            circleStu = next;

        }

        printf("index %d; studentName is %s;  point is %d\n",i,next->name,next->point);

        i++;

        next = next->stu;

    }

}

//查找循环链表中循环节点

Student * SelectCircleNodeInLinkTable(Student *student) {

    Student *fast = student;

    Student *slow = student;

    Student *circleStu = NULL;

    while (fast->stu) {

        fast = fast->stu->stu;//快指针节点 为慢指针节点的2倍

        slow = slow->stu;

        if (fast==NULL) { //不存在循环节点

            return NULL;

        }

        if (fast == slow) {//快慢指针相遇。找到循环节点

            circleStu = fast;

            break;

        }

    }

    if (fast==NULL) { //不存在循环节点

        return NULL;

    }

    printf("相遇节点为==%d\n",circleStu->point);

    fast=student;

    while (fast!=slow) {

        slow=slow->stu;

        fast=fast->stu;

    }

    return fast;

}

int main(void){

    char sf[];

//    /**

//     *  创建单向链表

//     */

//    int num;

//    printf ("请输入学生人数\n");

//    scanf("%d",&num);

//    Student *link_stu = CreateLink_Table(num);

//

//

//    /**

//     *  单向链表插入节点

//     */

//    printf ("请插入节点内容 在 已存在节点名字的后面，如 已存在节点名字|待插入名字|待插入分数 \n");

//    scanf("%s",sf);

//

//    link_stu = insertStudentLinkTable(link_stu,sf);

//

//    /**

//     *  反转单向链表

//     */

//    printf("反转链表Y|N \n");

//    scanf("%s",sf);

//    if (strcmp(sf,"Y")==0) {

//       Student *newLt= ReversionStudentLinkTable(link_stu);

//        //查询

//        selectStudent(newLt);

//    }

    /**

     *  创建循环链表

     */

    Student *student = NULL;

    printf("开始创建循环链表Y|N \n");

    scanf("%s",sf);

    if (strcmp(sf,"Y")==) {

      student =  CreateCircleLink_Table();

    }

    printf("已知情况查询循环链表Y|N \n");

    scanf("%s",sf);

    if (strcmp(sf,"Y")==) {

        SelectCircleLinkTable(student);

    }

    printf("未知情况查询循环链表Y|N \n");

    scanf("%s",sf);

    if (strcmp(sf,"Y")==) {

      Student *circleStu = SelectCircleNodeInLinkTable(student);

        printf("=====循环节点==%d\n",circleStu->point);

    }

    return ;

}