Count Smaller Numbers after Self

You are given an integer array nums and you have to return a new counts array. The counts array has the property where counts[i] is the number of smaller elements to the right of nums[i].

Example:

Given nums = [5, 2, 6, 1]

To the right of 5 there are 2 smaller elements (2 and 1).
To the right of 2 there is only 1 smaller element (1).
To the right of 6 there is 1 smaller element (1).
To the right of 1 there is 0 smaller element.

Return the array [2, 1, 1, 0].

Solution

class Solution(object):
    def countSmaller(self, nums):
        """
        :type nums: List[int]
        :rtype: List[int]
        """
        counts, sorted_array = [], []
        for i in range(len(nums)-1,-1,-1):
            counts.append(bisect.bisect_left(sorted_array, nums[i]))
            bisect.insort_left(sorted_array, nums[i])
        return counts[::-1]