题目描述： 编写一个程序，找到两个单链表相交的起始结点。
def getIntersectionNode(self,headA,headB): " " " :type head1,head:ListNode :rtype: ListNode " " " a=headA b=headB i=0 l=m=0 while a: a=a.next l+=1 while b: b=b.next m+=1 if a!=b: return None a=headA b=headB if l>m: diff=l-m while diff: a=a.next diff-=1 if l<m: diff=m-l while diff: b=b.next diff-=1 while a!=b: a=a.next b=b.next return a