public class Solution {
    public ListNode getIntersectionNode(ListNode headA, ListNode headB) {
         
        //怎么保证a链表上的指针下次指到b链表? 一轮就行了 不用考虑
         ListNode a = headA;
         ListNode b = headB;
         
         while(a != b){
            a = a == null ? headB : a.next;
            b = b == null ? headA : b.next;
         }
        return a;
    }
}