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.
Given nums = [1, 4, 8, 13], target = 12, Because nums[1] + nums[2] = 4 + 8 = 12, return [1, 2].
Solution:
