题目：

Write a program to find the node at which the intersection of two singly linked lists begins.

For example, the following two linked lists:

A:          a1 → a2                   ↘                     c1 → c2 → c3                   ↗            B:     b1 → b2 → b3

判断两个链表是否相交，表1和表2都按顺序往下走，若表1走完从2继续走，若表2走完从1继续走，然后两个经过（m+n）次总能找到相交的结点。

class Solution {public:    ListNode *getIntersectionNode(ListNode *headA, ListNode *headB) {        ListNode *ind1 = headA, *ind2 = headB;        while(ind1 != ind2){            ind1 = ind1?ind1->next:headB;            ind2 = ind2?ind2->next:headA;        }                return ind1;    }};