<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: List[int]) -> List[int]:
        items=[]
        ans=[0]*len(nums)
        for i in range(len(nums)):
            items.append((nums[i],i))
        self.mergeSort(items,ans,0,len(nums)-1)
        return ans
    def mergeSort(self,nums,ans,l,h):
        if l>=h:
            return
        mid=(l+h)//2
        self.mergeSort(nums,ans,l,mid)
        self.mergeSort(nums,ans,mid+1,h)
        self.merge(nums,ans,l,mid,h)
    def merge(self,items,ans,l,mid,h):
        i=l
        j=mid+1
        temp=[0]*(h-l+1)
        k=0
        f=0
        while i<=mid and j<=h:
            if items[i][0]<=items[j][0]:

                temp[k]=items[i]
                ans[items[i][1]]+=f
                k+=1
                i+=1
                
            else:
                temp[k]=items[j]
                j+=1
                k+=1
                f+=1
        while i<=mid:
            temp[k]=items[i]
                
            ans[items[i][1]]+=f
            k+=1
            i+=1
        while j<=h:
            temp[k]=items[j]
            j+=1
            k+=1
        k=0
        for i in range(l,h+1):
            items[i]=temp[k]
            k+=1




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