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 fast = pHead;
        ListNode slow = pHead;

        while (fast != null && fast.next != null) {
            fast = fast.next.next;
            slow = slow.next;

            if (fast == slow) {
                fast = pHead;

                while (fast != slow) {
                    fast = fast.next;
                    slow = slow.next;
                }

                return fast;
            }
        }

        return null;
    }
}