Given an array of integers nums and an integer target, return the indices of the two distinct elements whose values add up to target. The input is guaranteed to contain exactly one valid pair, and you may not use the same element twice. Return the indices in any order as a list of two integers.
Input: nums = [2, 7, 11, 15], target = 9
Output: [0, 1]
Explanation: nums[0] + nums[1] = 2 + 7 = 9.
Input: nums = [3, 2, 4], target = 6
Output: [1, 2]
Explanation: nums[1] + nums[2] = 2 + 4 = 6.
2 <= len(nums) <= 10^5-10^9 <= nums[i] <= 10^9-10^9 <= target <= 10^9