oop/LinkedList_Array/ConsoleApplication1/LinkedList.h

#pragma once
#include <iostream>

// Forward declaration of LinkedListNode
template <typename T> class LinkedListNode;

class LinkedListException {};
/// <summary>
/// Class representing a linked list
/// </summary>
/// <typeparam name="T">Value type</typeparam>
template <typename T> class LinkedList {
    bool isCircular;
    LinkedListNode<T>* start;

    /// <summary>
    /// Copies the linked list to another instance
    /// </summary>
    /// <param name="list">Pointer to original linked list</param>
    LinkedList(const LinkedList& list);

    /// <summary>
    /// Assignment operator override
    /// </summary>
    /// <param name="list">The original linked list to be copied</param>
    /// <returns>The copied linked list</returns>
    LinkedList& operator =(const LinkedList& list);

public:
    LinkedList();
    ~LinkedList();

    /// <summary>
    /// Get the starting node of the linked list
    /// </summary>
    /// <returns>First node of the list</returns>
    LinkedListNode<T>* getStart();

    /// <summary>
    /// Delete the first item
    /// </summary>
    void deleteFirst();

    /// <summary>
    /// Delete the item following the node
    /// </summary>
    /// <param name="ptr">The node before the item to delete</param>
    void deleteAfter(LinkedListNode<T>* ptr);

    /// <summary>
    /// Insert some value into the new node in the beginning
    /// </summary>
    /// <param name="data">The value to be inserted</param>
    void insertFirst(const T& value);

    /// <summary>
    /// Insert some value after the node
    /// </summary>
    /// <param name="ptr">The node after which the value shall be inserted</param>
    /// <param name="data">The value to be inserted</param>
    void insertAfter(LinkedListNode<T>* ptr, const T& value);

    /// <summary>
    /// Make the linked list circular (looped)
    /// </summary>
    void makeCircular();

    /// <summary>
    /// Output operator override
    /// </summary>
    /// <typeparam name="T">Some type</typeparam>
    /// <param name="out">Outbound stream</param>
    /// <param name="list">Linked list to be printed out</param>
    /// <returns>Outbound stream containing serialized values of the linked list</returns>
    template <typename U> friend std::ostream& operator <<(std::ostream& out, LinkedList<U>& list);
};

// Implementation of LinkedList

template <typename T> LinkedList<T>::LinkedList()
    : start(nullptr), isCircular(false) {}

template <typename T> LinkedList<T>::~LinkedList() {
    if (isCircular) {
        LinkedListNode<T>* current = start;
        while (current->_next != start) {
            current = current->_next;
        }
        current->_next = nullptr;
    }
    while (start) {
        deleteFirst();
    }
}

template <typename T> LinkedListNode<T>* LinkedList<T>::getStart() {
    return start;
}

template <typename T> void LinkedList<T>::deleteFirst() {
    if (start) {
        LinkedListNode<T>* temp = start->_next;
        delete start;
        start = temp;
    }
    else {
        throw LinkedListException();
    }
}

template <typename T> void LinkedList<T>::deleteAfter(LinkedListNode<T>* ptr) {
    if (ptr && ptr->_next) {
        if (ptr->_next == start) {
            LinkedListNode<T>* temp = ptr->_next;
            ptr->_next = ptr->_next->_next;
            delete temp;
            start = ptr->_next;
        }
        else {
            LinkedListNode<T>* temp = ptr->_next;
            ptr->_next = ptr->_next->_next;
            delete temp;
        }
    }
    else {
        throw LinkedListException();
    }
}

template <typename T> void LinkedList<T>::insertFirst(const T& value) {
    LinkedListNode<T>* second = start;
    start = new LinkedListNode<T>(value, second);
}

template <typename T> void LinkedList<T>::insertAfter(LinkedListNode<T>* ptr, const T& value) {
    if (ptr) {
        LinkedListNode<T>* temp = ptr->_next;
        ptr->_next = new LinkedListNode<T>(value, temp);
    }
}

template <typename T> std::ostream& operator<<(std::ostream& out, LinkedList<T>& list) {
    LinkedListNode<T>* ptr = list.getStart();
    if (!ptr) {
        out << "EMPTY ";
    }
    else {
        do {
            out << ptr->getValue() << ' ';
            ptr = ptr->getNext();
        } while (ptr && ptr != list.getStart());
    }
    return out;
}

template <typename T> void LinkedList<T>::makeCircular() {
    if (start == nullptr) {
        return;
    }

    LinkedListNode<T>* current = start;
    while (current->_next != nullptr) {
        current = current->_next;
    }

    current->_next = start;
    isCircular = true;
}