2.两数相加 golang

/**
 * Definition for singly-linked list.
 * type ListNode struct {
 *     Val int
 *     Next *ListNode
 * }
 */
func addTwoNumbers(l1 *ListNode, l2 *ListNode) *ListNode {
   if l1 == nil {
        return l2
    }
    if l2 == nil {
        return l1
    }
    sum := l1.Val + l2.Val
    jw := sum/10
    sum = sum%10
    head := &ListNode{sum,nil}
    tmp := head
    val1 := 0
    val2 := 0
    l1 = l1.Next
    l2 = l2.Next
    for l1 != nil || l2 != nil || jw != 0 {
        if l1 == nil {
            val1 = 0
        } else {
            val1 = l1.Val
            l1 = l1.Next
        }
        if l2 == nil {
            val2 = 0
        } else {
            val2 = l2.Val
            l2 = l2.Next
        }
        sum = val1 + val2 + jw
        jw = sum/10
        sum = sum%10
        tmp.Next = &ListNode{sum,nil}
        tmp = tmp.Next
    }
    return head
}