题解 | 链表中环的入口结点

import java.util.*;
/*
 public class ListNode {
    int val;
    ListNode next = null;

    ListNode(int val) {
        this.val = val;
    }
}
*/
public class Solution {

    public ListNode EntryNodeOfLoop(ListNode pHead) {
        /**
        思路分析：还是使用HashSet
         */
        ListNode temp = pHead;
        HashSet<ListNode> set = new HashSet<>();
        while(temp != null){
            if(set.contains(temp)){
                return temp;
            }
            set.add(temp);
            temp = temp.next;
        }
        return null;
    }
}