2.两数相加 Leecode每日分享

前提：python中 // 为取整

思路：仿照两个链表相加存储到第三个链表中，如果有进位，在末尾创建新节点并加上进位。

   def addTwoNumbers(l1, l2):
        """
        :type l1: ListNode
        :type l2: ListNode
        :rtype: ListNode
        """
        # 定义头节点和指针
        head = result = ListNode()
        # 进位标志
        advance = 0
        while l1 or l2:
            val = (l1.val if l1 else 0) + (l2.val if l2 else 0) + advance
            advance = val//10
            result.next = ListNode(val%10)
            result = result.next
            if l1:l1= l1.next
            if l2:l2= l2.next
            if advance:result.next = ListNode(advance)              
        return head.next