测试用例1500多个，考虑的情况非常多

测试用例

[0]  [1]    [2]  [3,4,2]  [5,0] [2]  [1]
[0]  [9,8]  [0]  [4,6,5]  [5,0] [1]  [9]
[0]  [0,9]  [2]  [8,0,7]  [0,1] [3]  [0,1]

func addTwoNumbers(l1 *ListNode, l2 *ListNode) *ListNode {result := &ListNode{}lastNode := resulttemp := 0for l1 != nil || l2 != nil || temp != 0 {//相加处理var v1, v2 intif l1 != nil {v1 = l1.Val//移位l1 = l1.Next} else {v1 = 0}if l2 != nil {v2 = l2.Val//移位l2 = l2.Next} else {v2 = 0}sum := v1 + v2 + temptemp = sum / 10bitNum := sum % 10//将数据添加到末端节点lastNode.Val = bitNum//是否准备新节点if l1 != nil || l2 != nil || temp != 0 {lastNode.Next = &ListNode{}} else {lastNode.Next = nil}lastNode = lastNode.Next}return result
}