Add Two Numbers

Problem page:https://leetcode.com/problems/add-two-numbers

Solution

class Solution(object):
        def addTwoNumbers(self, l1, l2):
            nHead = ListNode(0)
            tail = nHead
            carry = 0

            while l1 is not None or l2 is not None or carry != 0:
                d1 = l1.val if l1 is not None else 0
                d2 = l2.val if l2 is not None else 0

                sum = d1 + d2 + carry
                d = sum % 10
                carry = sum // 10

                nNode = ListNode(d)
                tail.next = nNode
                tail = tail.next

                l1 = l1.next if l1 is not None else None
                l2 = l2.next if l2 is not None else None

            res = nHead.next
            nHead.next = None
            return res

Complexity

• time: O(max(m,n))
• space: O(max(m,n))