牛客网：NC66 两个链表的第一个公共结点

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

    ListNode(int val) {
        this.val = val;
    }
}*/
public class Solution {
    public ListNode FindFirstCommonNode(ListNode node1, ListNode node2) {
        ListNode x = node1,  y = node2;
        while (x != y){
            x  = x == null ? node2 : x.next;
            y  = y == null ? node1 : y.next;
        }
        return x;
    }
}