0002. Add two numbers.py

class ListNode(object):
    def __init__(self, val=0, next=None):
        self.val = val
        self.next = next

class Solution(object):
    def addTwoNumbers(self,l1: ListNode,l2: ListNode) -> ListNode:
        dummy = ListNode()
        current = dummy

        carry = 0
        while l1 or l2 or carry:
            v1 = l1.val if l1 else 0
            v2 = l2.val if l2 else 0

            # new digit
            val = v1 + v2 + carry
            carry = val//10
            val = val%10
            current.next = ListNode(val)

            current = current.next
            l1 = l1.next if l1 else None
            l2 = l2.next if l2 else None
        
        return dummy.next

if __name__ == "__main__":
    pass