双指针进行遍历

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

    ListNode(int val) {
        this.val = val;
    }
}*/
public class Solution {
    public ListNode FindFirstCommonNode(ListNode pHead1, ListNode pHead2) {
        ListNode l1=pHead1;
        ListNode l2=pHead2;
        while(l1!=l2){
            l1=l1==null?pHead1:l1.next;
            l2=l2==null?pHead2:l2.next;

        }
        return l1;
 
    }
}