public boolean isSymmetricLevel(TreeNode left,TreeNode right){
        if(left == null && right == null)
            return true;
        if(left == null || right == null)
            return false;
        if(left.val != right.val)
            return false;
        return (isSymmetricLevel(left.left, right.right) && isSymmetricLevel(left.right,right.left));
    }