package leetcode

import (
	"github.com/halfrost/LeetCode-Go/structures"
)

// ListNode define
type ListNode = structures.ListNode

/**
 * Definition for singly-linked list.
 * type ListNode struct {
 *     Val int
 *     Next *ListNode
 * }
 */

func addTwoNumbers(l1 *ListNode, l2 *ListNode) *ListNode {
	if l1 == nil || l2 == nil {
		return nil
	}
	head := &ListNode{Val: 0, Next: nil}
	current := head
	carry := 0
	for l1 != nil || l2 != nil {
		var x, y int
		if l1 == nil {
			x = 0
		} else {
			x = l1.Val
		}
		if l2 == nil {
			y = 0
		} else {
			y = l2.Val
		}
		current.Next = &ListNode{Val: (x + y + carry) % 10, Next: nil}
		current = current.Next
		carry = (x + y + carry) / 10
		if l1 != nil {
			l1 = l1.Next
		}
		if l2 != nil {
			l2 = l2.Next
		}
	}
	if carry > 0 {
		current.Next = &ListNode{Val: carry % 10, Next: nil}
	}
	return head.Next
}