push_back.cpp

void push_back(const Data &data) noexcept
{
    // if the list is empty we're going to add head
    if (isEmpty())
    {
        head = std::make_unique<Node>(data, nullptr);
    }
    else
    {
        Node *current = head.get();
        while (current->next != nullptr)
        {
            current = current->next.get();
        }
        current->next = std::make_unique<Node>(data, nullptr);
    }
    size++;
}