LeetCode 2 – Python 3 (Week 06 – 15)

# Definition for singly-linked list.
# class ListNode:
#     def __init__(self, x):
#         self.val = x
#         self.next = None

class Solution:
    def addTwoNumbers(self, l1: ListNode, l2: ListNode) -> ListNode:
        if not l1: return l2
        if not l2: return l1
        
        carry = 0
        dummy = ListNode(0)
        p = dummy
        
        while l1 and l2:
            p.next = ListNode((l1.val + l2.val + carry) % 10)
            carry = (l1.val + l2.val + carry) // 10
            l1 = l1.next
            l2 = l2.next
            p = p.next
            
        while l1:
            p.next = ListNode((l1.val + carry) % 10)
            carry = (l1.val + carry) // 10
            l1 = l1.next
            p = p.next
            
        while l2:
            p.next = ListNode((l2.val + carry) % 10)
            carry = (l2.val + carry) // 10
            l2 = l2.next
            p = p.next
            
        if carry != 0:
            p.next = ListNode(carry)
            
        return dummy.next