Leetcode2-AddTwoNumbers

1. 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.

2. 分析

2.1 分解问题

• 需要将列表转换成单向链表形式
• 需要逐个相加
• 需要将链表打印出来

2.2 代码-python

from typing import List
from typing import Optional

# 定义节点，val表示节点的值
# next 表示下一个节点
class ListNode:
    def __init__(self, val=0, next=None):
        self.val = val
        self.next = next

# 定义方案
# 思路：
# 1. 定义一个记录的节点dummy
# 2. 定义一个循环的节点curr
# 3. 定义一个求和的carry
# 4. 逐位求和
# ５. 迭代循环

class Solution:
    def addTwoNumbers(self, l1: Optional[ListNode], l2: Optional[ListNode]) -> ListNode:

        dummy = ListNode(0)
        curr = dummy
        carry = 0

        while l1 or l2 or carry:
            if l1:
                carry += l1.val
                l1 = l1.next

            if l2:
                carry += l2.val
                l2 = l2.next

            curr.next = ListNode(carry % 10)
            carry //= 10
            curr = curr.next

        return dummy.next

    def createList(self, mylist: List) -> ListNode:
        output = ListNode(0)
        tmp = output
        for num in mylist:
            tmp.next = ListNode(num)
            tmp = tmp.next

        return output.next


def display(mylistnode: ListNode):
    print("[", end=" ")
    temp = mylistnode
    while temp.next:
        print(temp.val, end=" , ")
        temp = temp.next
    print(temp.val, end=" ")

    print("]")


if __name__ == "__main__":
    #    aa = [2, 4, 3]
    #    bb = [5, 6, 4]
    aa = [9, 9, 9, 9, 9, 9, 9]
    bb = [9, 9, 9, 9]
    myfun = Solution()
    list1 = myfun.createList(aa)

    list2 = myfun.createList(bb)

    result = myfun.addTwoNumbers(list1, list2)

    print(f"aa={aa}")

    print(f"bb={bb}")

    print(f"result=", end="")
    display(result)

aa=[9, 9, 9, 9, 9, 9, 9]
bb=[9, 9, 9, 9]
result=[ 8 , 9 , 9 , 9 , 0 , 0 , 0 , 1 ]

2.3 LeetCode 结果