<p>Given an integer array <code>nums</code>, return<em> an integer array </em><code>counts</code><em> where </em><code>counts[i]</code><em> is the number of smaller elements to the right of </em><code>nums[i]</code>.</p>

<p>&nbsp;</p>
<p><strong class="example">Example 1:</strong></p>

<pre>
<strong>Input:</strong> nums = [5,2,6,1]
<strong>Output:</strong> [2,1,1,0]
<strong>Explanation:</strong>
To the right of 5 there are <b>2</b> smaller elements (2 and 1).
To the right of 2 there is only <b>1</b> smaller element (1).
To the right of 6 there is <b>1</b> smaller element (1).
To the right of 1 there is <b>0</b> smaller element.
</pre>

<p><strong class="example">Example 2:</strong></p>

<pre>
<strong>Input:</strong> nums = [-1]
<strong>Output:</strong> [0]
</pre>

<p><strong class="example">Example 3:</strong></p>

<pre>
<strong>Input:</strong> nums = [-1,-1]
<strong>Output:</strong> [0,0]
</pre>

<p>&nbsp;</p>
<p><strong>Constraints:</strong></p>

<ul>
	<li><code>1 &lt;= nums.length &lt;= 10<sup>5</sup></code></li>
	<li><code>-10<sup>4</sup> &lt;= nums[i] &lt;= 10<sup>4</sup></code></li>
</ul>

class Solution:
    def countSmaller(self, nums):
        res = [0] * len(nums)

        num_ind = [(num,i) for i,num in enumerate(nums)]

        self.cnt_smaller(num_ind,0,len(num_ind)-1,res)

        return res

    def cnt_smaller(self,nums,left,right,res):
        if left>=right:
            return

        mid = (left+right)//2

        self.cnt_smaller(nums,left,mid,res)
        self.cnt_smaller(nums,mid+1,right,res)

        self.MnC(nums,left,mid,right,res)

    def MnC(self,nums,left,mid,right,res):
        i = left
        j = mid + 1
        temp_nums = []
        cnt = 0

        while i <= mid and j <= right:
            if nums[i][0] <= nums[j][0]:
                res[nums[i][1]] += cnt
                temp_nums.append(nums[i])
                i+=1
            else:
                cnt += 1
                temp_nums.append(nums[j])
                j+=1

        while i<= mid:
            res[nums[i][1]] += cnt
            temp_nums.append(nums[i])
            i += 1

        while j <= right:
            temp_nums.append(nums[j])
            j+=1

        nums[left:right+1] = temp_nums

sol = Solution()
print(sol.countSmaller([5, 2, 6, 1]))  # Output: [2, 1, 1, 0]
print(sol.countSmaller([-1, -1])) # Output: [0, 0]
print(sol.countSmaller([5,2,5,1]))
42395