445. 两数相加 II

package main
import "fmt"
type ListNode struct {
    Val  int
    Next *ListNode
}
func addTwoNumbers(l1 *ListNode, l2 *ListNode) *ListNode {
    l1 = revertNode(l1)
    l2 = revertNode(l2)
    dummyHead := &ListNode{Val: -1,}
    var carry int
    for l1 != nil || l2 != nil {
        var a int
        if l1 != nil {
            a = l1.Val
            l1 = l1.Next
        }
        var b int
        if l2 != nil {
            b = l2.Val
            l2 = l2.Next
        }
        sum := a + b + carry
        carry = sum / 10
        node := &ListNode{
            Val: sum % 10,
        }
        head := dummyHead.Next
        node.Next = head
        dummyHead.Next = node
    }
    if carry > 0 {
        node := &ListNode{
            Val: carry,
        }
        head := dummyHead.Next
        node.Next = head
        dummyHead.Next = node
    }
    return dummyHead.Next
}
func revertNode(l *ListNode) *ListNode {
    var pre *ListNode
    curr := l
    for curr != nil {
        next := curr.Next
        curr.Next = pre
        pre = curr
        curr = next
    }
    return pre
}
func main() {
    a1 :=  &ListNode{
         Val:  7,
     }
    b1 :=  &ListNode{
        Val:  2,
    }
    a1.Next = b1
    c1 :=  &ListNode{
        Val:  4,
    }
    b1.Next = c1
    d1 :=  &ListNode{
        Val:  3,
    }
    c1.Next = d1
    a2 :=  &ListNode{
        Val:  5,
    }
    b2 :=  &ListNode{
        Val:  6,
    }
    a2.Next = b2
    c2 :=  &ListNode{
        Val:  4,
    }
    b2.Next = c2
    r := addTwoNumbers(a1,a2)
    for r != nil{
        fmt.Println(r.Val)
        r = r.Next
    }
}