题解 | #链表中环的入口结点#

/*
 public class ListNode {
    int val;
    ListNode next = null;

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

    public ListNode EntryNodeOfLoop(ListNode pHead) {
        if (pHead == null) return null;
        if (pHead.next == null) return null;
        if (pHead.next == pHead) return pHead;
        ArrayList<ListNode> list = new ArrayList<>();
        while (pHead != null) {
            list.add(pHead);
            if (list.contains(pHead.next)) {
                return pHead.next;
            }
            pHead = pHead.next;
        }
        return null;
    }
}