445. Add Two Numbers II - LeetCode Solution

# Definition for singly-linked list.
# class ListNode:
#     def __init__(self, val=0, next=None):
#         self.val = val
#         self.next = next
class Solution:
    def addTwoNumbers(self, l1: ListNode, l2: ListNode) -> ListNode:
        h = []
        k = []
        
        while l1:
            h.append(str(l1.val))
            l1 = l1.next
        
        
        while l2:
            k.append(str(l2.val))
            l2 = l2.next
        
        h = int("".join(h))
        k = int("".join(k))
        
        h+=k
        h = list(str(h))
        
        head = ListNode()
        
        ptr = head
        
        for i in h:
            k = ListNode(i)
            
            ptr.next = k
            ptr = ptr.next
        
        return head.next