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) {
                // 处理入口逻辑
                ListNode n1 = pHead;
                ListNode n2 = fast;

                while(n1 != n2) {
                    n1 = n1.next;
                    n2 = n2.next;
                }
                return n1;
            }
        }
        return null;
    }
}