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.
You can return the answer in any order.
Example 1:
Input: nums = [2,7,11,15], target = 9Output: [0,1]Explanation: Because nums[0] + nums[1] == 9, we return [0, 1].
Example 2:
Input: nums = [3,2,4], target = 6Output: [1,2]
Example 3:
Input: nums = [3,3], target = 6Output: [0,1]
Constraints:
- `2 <= nums.length <= 104`
- `-109 <= nums[i] <= 109`
- `-109 <= target <= 109`
- Only one valid answer exists.
Follow-up: Can you come up with an algorithm that is less than `O(n2)` time complexity?
