Given an integer array nums and an integer target, return the indices of the two distinct elements whose sum equals target. Assume exactly one valid pair exists, and you may not use the same element twice.
Example 1:
Input: nums = [2, 7, 11, 15], target = 9
Output: [0, 1]
Explanation: nums[0] + nums[1] = 2 + 7 = 9
Example 2:
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