输入：l1 = [2,4,3], l2 = [5,6,4]输出：[7,0,8]解释：342 + 465 = 807.
输入：l1 = [0], l2 = [0]输出：[0]
输入：l1 = [9,9,9,9,9,9,9], l2 = [9,9,9,9]输出：[8,9,9,9,0,0,0,1]
func AddTwoNumbers(l1 *ListNode, l2 *ListNode) *ListNode {
node := new(ListNode)
head := node
incr := 0
//链表不为空或者进位的数不为0都要继续遍历
for l1 != nil || l2 != nil || incr > 0 {
value1 := 0
value2 := 0
if l1 != nil {
value1 = l1.Val
l1 = l1.Next
}
if l2 != nil {
value2 = l2.Val
l2 = l2.Next
}
sum := value1 + value2 + incr
if sum >= 10 {
sum = sum - 10
incr = 1
} else {
incr = 0
}
tmp := new(ListNode)
tmp.Val = sum
tmp.Next = nil
node.Next = tmp
node = tmp
}
return head.Next
}
