题解 | #链表中环的入口结点#

#include<iostream>
using namespace std;
/*
struct ListNode {
    int val;
    struct ListNode *next;
    ListNode(int x) :
        val(x), next(NULL) {
    }
};
*/
class Solution {
public:
    ListNode* EntryNodeOfLoop(ListNode* pHead) {
        int hashmap[10001]={0};
        ListNode* p=pHead;
        while(p)
        {
            if(hashmap[p->val]==0)
            hashmap[p->val]=1;
            else return p;
            p=p->next;
        }
        return nullptr;
    }
};