Leetcode 142. 环形链表II

目录

题目叙述

题解代码

 提交结果

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题目叙述

 

题解代码

class Solution {
public:
    ListNode *detectCycle(ListNode *head) {
    //设置快慢指针
    ListNode* fast = head;
    ListNode* slow = head;

    while(fast != NULL && fast->next != NULL){
        //慢指针一次走一步，快指针一次走两步
        slow = slow->next;
        fast = fast->next->next;
        //直到快慢指针相遇
        if(slow == fast)
        {
            ListNode* index1 = fast;
            ListNode* index2 = head;
            while(index1 != index2)
            {
                index1 = index1->next;
                index2 = index2->next;
            }
            return index2;
        }
    }
    return NULL;

    }
};

 提交结果