题解 | #链表中环的入口结点#

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

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

    public ListNode EntryNodeOfLoop(ListNode pHead) {
        Map<ListNode, Integer> map = new HashMap<>();
        while (pHead != null) {
            if (map.containsKey(pHead)) {
                return pHead;
            } else {
                map.put(pHead, 1);
                pHead = pHead.next;
            }
        }
        return null;
    }
}