void remove(const key_type &key) {
            Node *temp = findNode(key);
            Node *parent = temp->getParent();
            Node *leftChild = temp->getLeftChild();
            Node *rightChild = temp->getRightChild();

            if (root == nullptr) throw std::out_of_range("");

            // if node has no children
            if (!temp->hasChildren()) {
                if (parent == nullptr) {
                    root = nullptr;
                } else {
                    if (temp == parent->getLeftChild()) {
                        parent->setLeftChild(nullptr);
                    } else {
                        parent->setRightChild(nullptr);
                    }
                }
            } // has Left child only
            else if (leftChild != nullptr && rightChild == nullptr) {
                if (parent == nullptr) {
                    root = leftChild;
                    root->setParent(nullptr);
                } else {
                    if (temp == parent->getLeftChild()) {
                        parent->setLeftChild(leftChild);
                    } else {
                        parent->setRightChild(leftChild);
                    }
                    leftChild->setParent(parent);
                }
            } // has Right child only
            else if (rightChild != nullptr && leftChild == nullptr) {
                if (parent == nullptr) {
                    root = rightChild;
                    root->setParent(nullptr);
                } else {
                    if (temp == parent->getLeftChild()) {
                        parent->setLeftChild(rightChild);
                    } else {
                        parent->setRightChild(rightChild);
                    }
                    rightChild->setParent(parent);
                }
            } else {
                temp->setValue(rightChild->getValueType());

                remove(rightChild);

                --length;
                return;
            }

            --length;
            delete temp;
        }