Method balance

src/test/resources/pta/basic/RedBlackBST.java:240–249

(Node h)

    }

    private Node balance(Node h) {
        // assert (h != null);

        if (isRed(h.right) && !isRed(h.left)) h = rotateLeft(h);
        if (isRed(h.left) && isRed(h.left.left)) h = rotateRight(h);
        if (isRed(h.left) && isRed(h.right)) flipColors(h);

        h.size = size(h.left) + size(h.right) + 1;
        return h;
    }

    public int height() {
        return height(root);