main.go

package main

import "fmt"

type ListNode struct {
	Val  int
	Next *ListNode
}

func addTwoNumbers(l1 *ListNode, l2 *ListNode) *ListNode {
	if l1 == nil && l2 == nil {
		return nil
	}
	carry := 0

	var result *ListNode
	i := 0
	j := 0

	if l1 != nil {
		i = l1.Val
	}
	if l2 != nil {
		j = l2.Val
	}

	sum := i + j + carry

	if sum > 9 {
		carry = 1
	} else {
		carry = 0
	}

	sum %= 10

	var l1Next *ListNode
	var l2Next *ListNode

	if l1 != nil {
		l1Next = l1.Next
	}

	if l2 != nil {
		l2Next = l2.Next
	}

	if l1 != nil && l1.Next != nil {
		l1.Next.Val += carry
        carry = 0
	} else if l2 != nil && l2.Next != nil {
		l2.Next.Val += carry
        carry = 0
	}

	result = &ListNode{
		sum, addTwoNumbers(l1Next, l2Next),
	}

	if carry != 0 {
		result.Next = &ListNode{carry, nil}
	}

	return result
}

func main() {
	l1 := &ListNode{
		2, &ListNode{
			4, &ListNode{
				3, nil,
			},
		},
	}
	l2 := &ListNode{
		5, &ListNode{
			6, &ListNode{
				4, nil,
			},
		},
	}
	nodes := addTwoNumbers(l1, l2)
	for nodes != nil {
		fmt.Println(nodes.Val)
		nodes = nodes.Next
	}
}