Count Inversion

class Solution:
    def inversionCount(self, arr, n):
        temp=[0]*n
        return self._mergesort(arr,temp,0,n-1)
        
    def _mergesort(self,arr,temp,left,right):
        ic=0
        if (left < right):
            mid=(left+(right-left)//2)
            ic+=self._mergesort(arr,temp,left,mid)
            ic+=self._mergesort(arr,temp,mid+1,right)
            ic+=self.merge(arr,temp,left,mid,right)
        return ic
            
    def merge(self,arr,temp,left,mid,right):
        i=left
        j=mid+1
        k=left
        ic=0
        while(i <= mid and j <= right):
            if (arr[i] <= arr[j]):
                temp[k]=arr[i]
                k+=1
                i+=1
                
            else:
                temp[k]=arr[j]
                ic+=(mid-i+1)
                j+=1
                k+=1
                
        while(i <= mid):
            temp[k]=arr[i]
            i+=1
            k+=1
        while(j <= right):
            temp[k]=arr[j]
            j+=1
            k+=1
        for m in range(left,right+1):
            arr[m]=temp[m] 
        return ic