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