====== Objektový seznam (druhá část) ======

<code C++>
#include <iostream>
#undef NDEBUG
#include <cassert>
using namespace std;

class Item;

class List
{
private:
    Item * first;
    Item * last;
public:
    Item * getFirst () { return first; }
    Item * getLast () { return last; }
    bool empty () { return first == nullptr; }
private:
    void link (Item* before, Item* fresh, Item* after);
public:
    void linkFirst (Item* fresh);
    void linkLast (Item* fresh);

    void insertFirst (string name0, int r0, int g0, int b0);
    void insertLast  (string name0, int r0, int g0, int b0);

    Item * find (string name0);
    void   print ();

    List (); // konstruktor
    ~ List (); // destruktor

    friend class Item; 
};

class Item
{
public:
    string name;
    int    r, g, b;
private:
    List * above;
    Item * prev;
    Item * next;
public:
    Item* getPrev () { return prev; }
    Item* getNext() { return next; }
    List* getAbove() { return above; }

    void linkAfter (Item* fresh);
    void linkBefore (Item* fresh);

    void insertBefore (string name0, int r0, int g0, int b0);
    void insertAfter (string name0, int r0, int g0, int b0);

    void unlink ();

    Item (string name0 = "", int r0 = 255, int g0 = 255, int b0 = 255); // konstruktor
    ~Item ();

    friend class List;
};

// Item::Item() : name(""), r(255), g(255), b(255), prev(nullptr), next(nullptr) { }

Item::Item(string name0, int r0, int g0, int b0) : 
    name (name0), 
    r (r0), 
    g (g0), 
    b (b0), 
    above (nullptr),
    prev (nullptr),
    next (nullptr)
{ }

Item :: ~Item ()
{
    if (above != nullptr)
        unlink ();
}

List::List() // prazdny seznam
{
    first = nullptr;
    last = nullptr;
}

List :: ~ List  ()
{
    Item* p = first;
    while (p != nullptr)
    {
        Item* t = p->next;
        delete p;
        p = t;
    }
    // first = nullptr;
    // last = nullptr;
}

void List::link (Item* before, Item* fresh, Item* after)
{
    assert (before == nullptr || before->above == this && before->next == after); // before nulove nebo z naseho seznamu, nenulove before ma za naslednika after
    assert (after == nullptr || after->above == this && after->prev == before); // after nulove nebo z naseho seznamu, nenulove after ma za predchudce before

    assert (fresh != nullptr); // test zda fresh existuje
    assert (fresh->above == nullptr); // test zda fresh neni v zadnem seznamu

    fresh->above = this; // fresh zaradime do naseho seznamu

    fresh->prev = before;
    fresh->next = after;

    if (before != nullptr)
        before->next = fresh;
    else
        first = fresh;

    if (after != nullptr)
        after->prev = fresh;
    else
        last = fresh;
}

void List::linkFirst (Item* fresh)
{
    this->link (nullptr, fresh, this->first);
}

void List::linkLast (Item* fresh)
{
    link (last, fresh, nullptr);
}

void List::insertFirst (string name0, int r0, int g0, int b0)
{
    this->linkFirst (new Item (name0, r0, g0, b0));
}

void List::insertLast (string name0, int r0, int g0, int b0)
{
    linkLast (new Item (name0, r0, g0, b0));
}


void Item::linkAfter (Item* fresh)
{
    assert (above != nullptr);
    above->link (this, fresh, this->next);
}

void Item::linkBefore (Item* fresh)
{
    assert (above != nullptr);
    above->link (prev, fresh, this);
}

void Item::insertBefore (string name0, int r0, int g0, int b0)
{
    linkBefore (new Item (name0, r0, g0, b0));
}

void Item::insertAfter (string name0, int r0, int g0, int b0)
{
    linkAfter (new Item (name0, r0, g0, b0));
}

void Item::unlink ()
{
    assert (above != nullptr);

    Item* before = prev;
    Item* after = next;

    if (before != nullptr)
        before->next = after;
    else
        above->first = after;

    if (after != nullptr)
        after->prev = before;
    else
        above->last = before;

    prev = nullptr;
    next = nullptr;
    above = nullptr;
}

Item * List::find (string name0)
{
    Item * p = first;
    while (p != nullptr && p->name != name0)
    {
        p = p->next;
    }
    return p;
}

void List::print ()
{
    Item * t = first;
    while (t != nullptr)
    {
        cout << t->name << " " << t->r << "," << t->g << "," << t->b << endl;
        t = t->next;
    }
}

int main()
{
    List b; // promenna pro nas seznam

    b.insertLast ("cervena", 255, 0, 0);
    b.insertLast ("zelena", 0, 255, 0);
    b.insertLast ("modra", 0, 0, 255);

    Item * t = b.find ("zelena");
    if (t == nullptr)
        cout << "nenasli" << endl;
    else
    {
        cout << "nasli " << t->name << ", " << t->r << ", " << t->g << ", " << t->b << endl;
        t->insertBefore ("svetle " + t->name, 128, t->g, 128);
        // b.remove (t);
    }

    cout << endl;
    b.print ();

    List c;
    while (! b.empty ())
    {
        Item* t = b.getFirst ();
        t->unlink ();
        c.linkFirst (t);
    }

    cout << endl;
    c.print ();

    return 0;
}
</code>