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.
checklist Constraints
2 <= nums.length <= 10^4 -10^9 <= nums[i] <= 10^9 -10^9 <= target <= 10^9 Only one valid answer exists.