[1] Two Sum
Easy array hash-table
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].
解答 本题可以采用常规的方法和基于 hashtab 的方式进行处理(题目描述中已经定义不存在重复的数据)