LeetCode 2. Add Two Numbers

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You are given two non-empty linked lists representing two non-negative integers. The digits are stored in reverse order and each of their nodes contain a single digit. Add the two numbers and return it as a linked list.

You may assume the two numbers do not contain any leading zero, except the number 0 itself.

Input: (2 -> 4 -> 3) + (5 -> 6 -> 4)

Output: 7 -> 0 -> 8

Definition

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

class Solution(object):
    def addTwoNumbers(self, l1, l2):
        """
        :type l1: ListNode
        :type l2: ListNode
        :rtype: ListNode
        """

Solution

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class Solution(object):
    def addTwoNumbers(self, l1, l2):
        l = ListNode(0)
        p = ListNode(0)
        flag = 0
        while l1 or l2 or flag:
            if not l1:
                l1 = ListNode(0)
            if not l2:
                l2 = ListNode(0)
            p.next  = ListNode((l1.val + l2.val + flag)%10)
            flag = (l1.val + l2.val + flag)/10
            p = p.next
            l1 = l1.next
            l2 = l2.next
        return l.next