1. Description
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] = 9, return [0, 1]
2.How to deal with
Related algorithm: Brute Froce（简单匹配算法）
记被匹配的串为a，要匹配的串为b。从b的第一个元素b0开始，与a的元素a0。若匹配，则接下来匹配b1与a1，若不匹配，则b元素往后退一个，与a的第一个元素开始匹配起，以此往后推。若匹配成功，返回成功匹配的a的第一个元素index，若匹配失败，则返回-1.