LinkedList add operation

linkedListAddOperation.hpp

/**
 * Add a new item to the data structure.
 *
 * @tparam T type
 * @param item the new item
 */
template<typename T>
void LinkedList<T>::add(const T &item) {
    // Create a box which wraps the new element.
    auto *const newNode = new Node<T>(item);

    if (!_head) {
        // If the head is NULL then the data structure is empty,
        // so make the first element (the head) be the new element.
        // Do the same for the tail element.
        _head = newNode;
        _tail = newNode;

        // Increase the size of the data structure.
        ++_size;
    } else {
        // If the head is not null, then we have some elements
        // to work with and also the tail is not null.

        // Attach the new node to the last element (the tail) and
        // make it the new tail.
        _tail->next = newNode;
        _tail = newNode;

        // Increase the size of the data structure.
        ++_size;
    }
}