Given an array of integers `nums` and an integer `target`, return **indices** of the two numbers such that they add up to `target`. You may assume that each input would have **exactly one solution**, and you may not use the same element twice.
Input: nums = [2,7,11,15], target = 9
Output: [0,1]
nums[0] + nums[1] = 2 + 7 = 9
Input: nums = [3,2,4], target = 6
Output: [1,2]