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) {
        Set<ListNode> set = new HashSet<ListNode>();
        while(pHead!= null){
            if(set.contains(pHead)){
                return pHead;
            }else{
                set.add(pHead);
            }
            pHead = pHead.next;
        } 
        return null;
    }
}