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) {
        if(pHead1==null)return null;
        if(pHead2==null) return null;
        ListNode tm1 = pHead1;
        ListNode tm2 = pHead2;
        //    if(pHead1.next.next.next==pHead2.next.next){
        //     return null;
        //    }
        while (pHead1 != pHead2) {
            pHead1 = pHead1.next;
            pHead2 = pHead2.next;
            if(pHead1==null&&pHead2==null){
                return null;
            }
            if (pHead1 == null) {
                pHead1 = tm2;
            }
            if (pHead2 == null) {
                pHead2 = tm1;
            }

        }
        return pHead1;
    }
}

//我看了题解