README.md

315. Count of Smaller Numbers After Self

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 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.

Example 2:

Input: nums = [-1]
Output: [0]

Example 3:

Input: nums = [-1,-1]
Output: [0,0]

Constraints:

• 1 <= nums.length <= 105
• -104 <= nums[i] <= 104

Solutions (Python)

1. Solution

from sortedcontainers import SortedList


class Solution:
    def countSmaller(self, nums: List[int]) -> List[int]:
        sortednums = SortedList()
        counts = [0] * len(nums)

        for i in range(len(nums) - 1, -1, -1):
            counts[i] = sortednums.bisect_left(nums[i])
            sortednums.add(nums[i])

        return counts