iterator begin() {
        Node* cr = this->root;
        bool flag = false;
        while (cr && !flag) {
            if (cr->left && !cr->leftThreaded) {
                cr = cr->left;
            }
            else flag = true;
        }
        return iterator(cr, this);
    }

    /*Returns an iterator to the node that follows the node with the biggest value.*/
    iterator end() {
        return iterator(nullptr, this);
    }

    /*Returns a const_iterator that points to the node with the smallest value.*/
    const_iterator cbegin()const {
        Node* cr = this->root;
        bool flag = false;
        while (cr && !flag) {
            if (cr->left && !cr->leftThreaded) {
                cr = cr->left; //if the node has a left child -> move left
            }
            else flag = true;
        }
        return const_iterator(cr, this);
    }

    /*Returns a const_iterator to the node that follows the node with the biggest value.*/
    const_iterator cend() const {
        return const_iterator(nullptr, this);
    }