LeetCode : Two sum

Posted 2020-09-01

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].

题意：
就是给一个数组，找到两个元素的值之和为给定值，返回元素下标

分析：
最直接的做法就是暴力，但是时间复杂度肯定不行，然后想到用哈希，以空间换时间即可,先将数组转换为哈希表即可

python代码

class Solution(object):
    def twoSum(self, nums, target):
        if len(nums) <= 1:
            return False
        buff_dict = {}
        for i in range(len(nums)):
            if nums[i] in buff_dict:
                return [buff_dict[nums[i]], i]
            else:
                buff_dict[target - nums[i]] = i