本题关键:
a+c+b=b+c+a
// 243 h160 相交链表public ListNode getIntersectionNode(ListNode headA, ListNode headB) {ListNode pointA=headA,pointB=headB;int rount=2;while (rount>0){if (pointA==pointB){return pointA;}pointA=pointA.next;pointB=pointB.next;if (pointA==null){pointA=headB;rount--;}if (pointB==null){pointB=headA;}}return null;}