1. 题目描述

2. 解题思路

3. 代码实现

/*
struct ListNode {int val;struct ListNode *next;ListNode(int x) :val(x), next(NULL) {}
};
*/
class Solution {
public:ListNode* hasCycle(ListNode *head) {if(head == nullptr) return nullptr;ListNode* fast = head, *slow = head;while(fast && slow && fast->next){fast = fast->next->next;slow = slow->next;if(fast == slow) return fast;}return nullptr;}ListNode* EntryNodeOfLoop(ListNode* head) {ListNode* meet = hasCycle(head);if(meet){ListNode* cur = head;while(cur != meet){cur = cur->next;meet = meet->next;}return meet;}return nullptr;}
};