LeetCode（Python3）1.两数之和 2.两数相加

目录

两数之和

两数相加

两数之和

Question：

Given an array of integers nums and an integer target, return indices of the two numbers such that they add up to target.

You may assume that each input would have exactly one solution, and you may not use the same element twice.

You can return the answer in any order.

Example1：

Example2： 

Example3:

Mentality ：

Code：

from typing import List

nums = [3, 3]
target = 6

def twoSum(nums: List[int], target: int) -> List[int]:
    result = {}
    for index, num in enumerate(nums):
        another = target - num
        if another in result:
            return [result[another], index]
        result[num] = index
    return None

print(twoSum(nums, target))

Result：

两数相加

Question：

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.

Example1： 

Example2：

Mentality：

 Code：

# Definition for singly-linked list.
class ListNode:
    def __init__(self, val=0, next=None):
        self.val = val
        self.next = next
        
class Solution:
    def addTwoNumbers(self, l1: ListNode, l2: ListNode) -> ListNode:
        l3 =  ListNode(-1)
        head = l3
        step = 0
        while l1 or l2 or step:
            x = l1.val if l1 else 0
            y = l2.val if l2 else 0
            result = x + y +step
            result, step = result % 10, result // 10
            head.next = ListNode(result)
            head = head.next
            l1 = l1.next if l1 else None
            l2 = l2.next if l2 else None
        return l3.next

Result：