mufengcoding 的博客

很简单的一道题目：

1.Two Sum

Given an array of integers, return**indices**of the two numbers such that they add up to a specific target.

You may assume that each input would have**_exactly_**one solution, and you may not use the_same_element twice.

Example:

Given nums = [2, 7, 11, 15], target = 9,

Because nums[0] + nums[1] = 2 + 7 = 9,
return [0, 1].

第一次写的：

class Solution:
    def twoSum(self, nums, target: int) :
        for i in range(0,len(nums)):
            for j in range(i+1,len(nums)):
                if  i!=j and nums[i] + nums[j] == target:
                    return [i,j]

当list很大的时候很很慢，而且没有那么复杂😳

第二次写的：

class Solution:
    def twoSum(self, nums: List[int], target: int) -> List[int]:
        for i in range(0,len(nums)):
            if target - nums[i] in nums: 
                if i !=  nums.index(target - nums[i]) :               
                    return [i,nums.index(target - nums[i]) ]

性能大大提高，如果换做是你 ，你会怎么做？

这是题库中的第一题，也是最简单的一题，受挫