Add Two Numbers 两个链表相加 python

描述：

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

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

Output: 7 -> 0 -> 8

python 2.7.x环境，代码如下：

# coding=utf-8


class LinkNode(object):  # 定义链表节点
    def __init__(self, val, nextnode=None):
        self.val = val
        self.nextnode = nextnode


class Solution(object):
    def add_two_list(self, lista=None, listb=None):
        if lista is None:
            return listb
        if listb is None:
            return lista
        ret = LinkNode(0)
        p = ret
        cflag = 0
        while lista or listb:  # 直接把两个链表的长短不一考虑进来
            total = cflag
            if lista:
                total += lista.val
                lista = lista.nextnode
            if listb:
                total += listb.val
                listb = listb.nextnode
            p.nextnode = LinkNode(total % 10)
            cflag = total / 10
            p = p.nextnode
        if cflag == 1:
            p.nextnode = LinkNode(1)
        return ret.nextnode
if __name__ == '__main__':
    roota = LinkNode(2)
    node1 = LinkNode(4)
    node2 = LinkNode(3)
    roota.nextnode = node1
    node1.nextnode = node2
    rootb = LinkNode(5)
    node3 = LinkNode(6)
    node4 = LinkNode(4)
    rootb.nextnode = node3
    node3.nextnode = node4
    out = Solution().add_two_list(roota, rootb)
    while out:
        print out.val
        out = out.nextnode