【leetcode刷题】20T2-两数相加

示例：
输入：(2 -> 4 -> 3) + (5 -> 6 -> 4)
输出：7 -> 0 -> 8
原因：342 + 465 = 807

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

class Solution(object):
    def deal_forward(self, val):
        # 处理进位
        add_one = 0
        if val >= 10:
            add_one = 1
        val = val % 10
        return val, add_one

    def addTwoNumbers(self, l1, l2):
        """
        :type l1: ListNode
        :type l2: ListNode
        :rtype: ListNode
        """
        add_one = 0
        h1, h2 = l1, l2
        l3, h3 = None, None

        # 相加
        while h1 and h2:
            val = h1.val + h2.val + add_one
            val, add_one = self.deal_forward(val)

            h1, h2 = h1.next, h2.next
            if h3 is None:
                h3 = ListNode(val)
                l3 = h3
            else:
                h3.next = ListNode(val)
                h3 = h3.next

        # 剩余部分
        while h1:
            val = h1.val + add_one
            val, add_one = self.deal_forward(val)
            h1 = h1.next
            h3.next = ListNode(val)
            h3 = h3.next

        while h2:
            val = h2.val + add_one
            val, add_one = self.deal_forward(val)
            h2 = h2.next
            h3.next = ListNode(val)
            h3 = h3.next

        if add_one != 0:
            h3.next = ListNode(add_one)

        return l3