# 100DaysLeetcode(1)

You are given two non-empty linked lists representing two non-negative integers. The digits are stored in reverse order and each of their nodes contain a single digit. Add the two numbers and return it as a linked list.

You may assume the two numbers do not contain any leading zero, except the number 0 itself.

``````Input: (2 -> 4 -> 3) + (5 -> 6 -> 4)
Output: 7 -> 0 -> 8
Explanation: 342 + 465 = 807.
``````

# Solution

``````public class ListNode {
public var val: Int
public var next: ListNode?
public init(_ val: Int) {
self.val = val
self.next = nil
}
}

func addTwoNumbers(_ l1: ListNode?, _ l2: ListNode?) -> ListNode? {
if l1 == nil, l2 == nil {
return nil
}

var l1 = l1, l2 = l2
var carry = 0
while l1 != nil || l2 != nil {
let sum = (l1?.val ?? 0) + (l2?.val ?? 0) + carry
carry = sum/10
nextNode.val = sum%10
l1 = l1?.next
l2 = l2?.next
if l1 == nil, l2 == nil {
if carry > 0 {
let node = ListNode(1)
nextNode.next = node
break
}
}else {
let node = ListNode(0)
nextNode.next = node
nextNode = node
}
}