Given an integer array `nums`, return an integer array `counts` where `counts[i]` is the number of smaller elements to the right of `nums[i]`.
Example 1
Input:nums = [5,2,6,1]
Output:[2,1,1,0]
Explanation:To the right of 5 there are 2 smaller (2 and 1). To the right of 2 there is 1 smaller (1). To the right of 6 there is 1 smaller (1). To the right of 1 there are 0.