private static Tree convertTree(int[] arr, int start, int end) {

        //base case
        if (start > end )
            return null;
        int mid = start + end;
        if( mid % 2 == 0 )
            mid = mid / 2;
        else
            mid = ( mid / 2 ) + 1;
        Tree root = new Tree(arr[mid]);
        root.left = convertTree(arr, start, mid - 1);
        root.right = convertTree(arr, mid + 1, end );

        return root;
}