0002 - Add Two Number

Python Leetcode 问题: 0002 - Add Two Number

题目

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 contains a single digit. Add the two numbers and return the sum as a linked list.

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

传入 数字列表 及 最后答案加总数值，回传 最后答案加总数值 是 数字列表 的第几个跟第几个数字的加总

答案

from typing import List


class ListNode(object):
    def __init__(self, x):
        self.val = x
        self.next = None


class Solution:
    @staticmethod
    # ListNode 转换成数字清单
    def listNodeToNumList(HeadListNode: ListNode) -> List[int]:
        # 数字清单
        num_list = []
        while HeadListNode is not None:
            num_list.append(HeadListNode.val)
            HeadListNode = HeadListNode.next

        return num_list

    @staticmethod
    # 数字清单转换成 ListNode
    def numListToListNode(nums_list: List[int]) -> ListNode:
        # 初始化链结节点
        HeadListNode = ListNode(None)

        # 设定目前链结节点
        CurrentListNode = HeadListNode
        for value in nums_list:
            # 设定链结节点的下一节点
            CurrentListNode.next = ListNode(value)
            # 将下一节点设为目前节点
            CurrentListNode = CurrentListNode.next

        return HeadListNode.next

    def addTwoNumbers(self, FirstNumberListNode: ListNode, SecondNumberListNode: ListNode) -> ListNode:
        # 建立答案节点，预设个位数是 0
        AnswerListNode = ListNode(0)
        CurrentAnswerListNode = AnswerListNode  # 目前答案节点
        number_1: int = 0  # 第 1 个加总数值
        number_2: int = 0  # 第 2 个加总数值
        carry_number: int = 0  # 加总后的进位数值
        number_sum: int = 0  # 加总数值

        while FirstNumberListNode is not None or SecondNumberListNode is not None or carry_number != 0:
            # === 计算第 1 个数字 ===
            if FirstNumberListNode is None:
                # 若「第 1 数字节点」为 nil，表示没有数字可以做加总了，设定可加总数字为 0
                number_1 = 0
            else:
                # 若「第 1 数字节点」有值，将节点数值设定为此次第 1 个加总数值
                number_1 = FirstNumberListNode.val
                FirstNumberListNode = FirstNumberListNode.next

            # === 计算第 2 个数字 ===
            if SecondNumberListNode is None:
                # 若「第 2 数字节点」为 nil，表示没有数字可以做加总了，设定可加总数字为 0
                number_2 = 0
            else:
                number_2 = SecondNumberListNode.val
                SecondNumberListNode = SecondNumberListNode.next

            # 加总数值
            number_sum = number_1 + number_2 + carry_number
            # 设定馀数为目前答案节点数值
            CurrentAnswerListNode.next = ListNode(number_sum % 10)
            # 设定答案节点的下一节点为目前节点，继续往后做加总
            CurrentAnswerListNode = CurrentAnswerListNode.next
            # 取得加总后的进位数值，继续往后做加总
            carry_number = int(number_sum / 10)

        return AnswerListNode.next


if __name__ == '__main__':
    # begin
    s = Solution()
    print(s.listNodeToNumList(s.addTwoNumbers(s.numListToListNode([2, 4, 3]), s.numListToListNode([5, 6, 4]))))
    print(s.listNodeToNumList(
        s.addTwoNumbers(s.numListToListNode([9, 9, 9, 9, 9, 9, 9]), s.numListToListNode([9, 9, 9, 9]))))

0002 - Add Two Number

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