[Question]: – Add two numbers using the ListList in swift.
Ex Input: l1 = [2,4,3], l2 = [5,6,4] Output: [7,0,8] Explanation: 342 + 465 = 807.

``````//Definition for singly-linked list.
public class ListNode {
public var val: Int
public var next: ListNode?
public init() { self.val = 0; self.next = nil; }
public init(_ val: Int) { self.val = val; self.next = nil; }
public init(_ val: Int, _ next: ListNode?) { self.val = val; self.next = next; }
}
extension ListNode: CustomStringConvertible {

public var description: String {
guard let next = next else {
return "\(val)"
}
return "\(val) -> " + String(describing: next) + " "
}
}

private var reminderVal = 0
func addTwoNumbers(_ l1: ListNode?, _ l2: ListNode?) -> ListNode? {
if l1 == nil && l2 == nil && reminderVal == 0 { return nil }
let sum = (l1?.val ?? 0) + (l2?.val ?? 0) + reminderVal
reminderVal = sum / 10 // ex 10/10 = 1 so add it two next iteration.
return .init(sum % 10, addTwoNumbers(l1?.next, l2?.next))
}
let l1 = ListNode(2, ListNode(4, ListNode(3)))
let l2 = ListNode(5, ListNode(6, ListNode(4)))