一:题目

二:思路分析

三:上码

class Solution {
public:ListNode *detectCycle(ListNode *head) {ListNode* slow = head;ListNode* fast = head;while (fast != NULL && fast->next != NULL && fast->next->next != NULL) {//这里选用快指针fast = fast->next->next;              //因为快指针是最快到达尾结点的slow = slow->next;//相遇了if (fast == slow) {ListNode* index1 = fast;ListNode* index2 = head;while (index1 != index2) {index1 = index1->next;index2 = index2->next;} return index1;}}return NULL;}
};

我下次一定好好弄思路 ipad随手写，然后就是随手导出的 啊啊啊啊啊呜呜呜呜呜