10min，一次通過(guò)

class Solution(object):
    def getIntersectionNode(self, headA:ListNode, headB:ListNode):
        """
        :type head1, head1: ListNode
        :rtype: ListNode
        """
        cnt1,cnt2=0,0
        cur=headA
        while cur:
            cnt1+=1
            cur=cur.next
        cur=headB
        while cur:
            cnt2+=1
            cur=cur.next
        while cnt1>cnt2:
            headA=headA.next
            cnt1-=1
        while cnt1<cnt2:
            headB=headB.next
            cnt2-=1
        while headA and headB!=headA: # 沒(méi)有公共節(jié)點(diǎn)
            headB=headB.next
            headA=headA.next
        return headA

考慮到了兩個(gè)都為空，沒(méi)有公共節(jié)點(diǎn)的情況，很好，一次通過(guò)