445 Add Two Numbers II

Python

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

class Solution(object):
    def reverseList(self, head):
        prev, curr = None, head
        while curr:
            t = curr.next
            curr.next = prev
            prev = curr
            curr = t
        return prev

    def addTwoNumbers(self, l1, l2):
        """
        :type l1: ListNode
        :type l2: ListNode
        :rtype: ListNode
        """
        l1 = self.reverseList(l1)
        l2 = self.reverseList(l2)
        cur, carry = 0, 0
        head = ListNode(0)
        curNode = head

        while l1 or l2:
            x = l1.val if l1 else 0
            y = l2.val if l2 else 0
            cur = x + y + carry
            carry = cur / 10
            cur = cur % 10 
            curNode.next = ListNode(cur)
            curNode = curNode.next
            if l1:
                l1 = l1.next
            if l2: 
                l2 = l2.next

        if carry:
            curNode.next = ListNode(carry)
            curNode = curNode.next

        return self.reverseList(head.next)