template <class T>
const Node<T> *BinaryTree<T>::find_const(const T &element, const Node<T> *node) const {
    if (node->get_element() == element) return node;
    if (node->left) {
        const Node<T> *node1 = nullptr;
        if (node1 = find_const(element, node->left))
            return node1;
        if (node->right) {
            if (node1 = find_const(element, node->right))
                return node1;
        }
    }
    return nullptr;
}


template <class T>
void BinaryTree<T>::map_element(BinaryTree<T> *tree, const Node<T> *node, T(*func)(const T &)) const{
    if (node) {
        tree->add(func(node->get_element()));
        if (node->left) {
            map_element(tree, node->left, func);
            if (node->right)
                map_element(tree, node->right, func);
        }
    }
}

template <class T>
void BinaryTree<T>::where_element(BinaryTree<T> *tree, const Node<T> *node, bool(*func)(const T &)) const {
    if (node) {
        if (func(node->get_element()))
            tree->add(node->get_element());
        if (node->left) {
            where_element(tree, node->left, func);
            if (node->right)
                where_element(tree, node->right, func);
        }
    }
}

template <class T>
void BinaryTree<T>::concat_element(BinaryTree<T> *tree, const Node<T> *node) const{
    if (node) {
        tree->add(node->get_element());
        if (node->left) {
            concat_element(tree, node->left);
            if (node->right)
                concat_element(tree, node->right);
        }
    }
}

template <class T>
void BinaryTree<T>::map(BinaryTree<T> *tree, T(*func)(const T &)) const {
    if (!tree) {
        cout << "Nullptr passed as destination tree." << endl;
        return;
    }
    if (!func) {
        cout << "Nullptr passed as function." << endl;
        return;
    }
    if (tree->get_size() != 0) {
        cout << "Destination tree wasn't empty and was cleared." << endl;
        tree->clear();
    }
    map_element(tree, root, func);
}

template <class T>
void BinaryTree<T>::where(BinaryTree<T> *tree, bool(*func)(const T &)) const {
    if (!tree) {
        cout << "Nullptr passed as destination tree." << endl;
        return;
    }
    if (!func) {
        cout << "Nullptr passed as function." << endl;
        return;
    }
    if (tree->get_size() != 0) {
        cout << "Destination tree wasn't empty and was cleared." << endl;
        tree->clear();
    }
    where_element(tree, root, func);
}

template <class T>
void BinaryTree<T>::concat(BinaryTree<T> *tree) const {
    if (!tree) {
        cout << "Nullptr passed as destination tree." << endl;
        return;
    }
    concat_element(tree, root);
}