Linked List insert operation

linkedListInsertOperation.hpp

/**
 * Insert an element to the data structure at a specified index.
 *
 * @tparam T type
 * @param item item to insert
 * @param index index at which to insert
 */
template<typename T>
void LinkedList<T>::insert(const T &item, const int index) {
    if (index < 0 || index >= _size) {
        // If the index is out of bounds, throw an exception.
        throw std::invalid_argument("Index out of bounds");
    } else {
        // Create a box which wraps the new element.
        auto *const newNode = new Node<T>(item);

        // Initialize an index counter and two pointers to
        // track two consecutive elements.
        int indexCounter = 0;
        Node<T> *prev = nullptr;
        Node<T> *iter = _head;

        // While we haven't reached the desired index,
        // move both element pointers to the right.
        while (indexCounter++ < index) {
            prev = iter;
            iter = iter->next;
        }

        if (prev && iter) {
            // If we have both pointers pointing to an element,
            // then we're somewhere after the first element in the
            // data structure, so make the current element's previous
            // point to the new element and make the new element point
            // to the current one.
            prev->next = newNode;
            newNode->next = iter;

            // Increase the data structure's size.
            ++_size;
        } else if (iter) {
            // If only the pointer to the current element is
            // not null, then we're at the first element of the
            // data structure (the head), so make the new element
            // be the head and point it to the old head element.
            _head = newNode;
            _head->next = iter;

            // Increase the data structure's size.
            ++_size;
        }
    }
}