Count Inversions in an array

int _mergeSort(int arr[], int temp[], int left, int right)
{
  int mid, inv_count = 0;
  if (right > left)
  {
     mid = (right + left)/2;
  
     inv_count  = _mergeSort(arr, temp, left, mid);
     inv_count += _mergeSort(arr, temp, mid+1, right);
     inv_count += merge(arr, temp, left, mid+1, right);
  }
  return inv_count;
}
  
int merge(int arr[], int temp[], int left, int mid, int right)
{
  int i, j, k;
  int inv_count = 0;
  
  i = left;
  j = mid; 
  k = left;
  while ((i <= mid - 1) && (j <= right))
  {
    if (arr[i] <= arr[j])
    {
      temp[k++] = arr[i++];
    }
    else
    {
      temp[k++] = arr[j++];
    }
      inv_count += (mid - i);
    }
  }
  
  while (i <= mid - 1)
    temp[k++] = arr[i++];
  
  while (j <= right)
    temp[k++] = arr[j++];
  
  for (i=left; i <= right; i++)
    arr[i] = temp[i];
  
  return inv_count;
}