С++ все про списки односвязные списки v3

https://youtu.be/aBidgQ0xZSk

#include <iostream>
#include <string>
using namespace std;
class Node
{
    string FirstName;
    //string LastName;
    //string MiddleName;
    class Node *ptr;
    friend class List;
};

class List
{
    Node *head;
    int count = 0;
    Node* Prev(Node *); // Переход к предыдущему узлу (не интерфейсный метод)
public:
    List() { head = NULL; } // Инициализация списка
    int getCount() { return count; } // Получение количества узлов списка
    bool isEmpty() { return head == NULL; }  // Проверка, пуст ли список
    string getValue(Node* p) { return p->FirstName; } // Получение значения узла списка
    //string getValue2(Node* p) { return p->LastName; } // Получение значения 2го узла списка
    //string getValue3(Node* p) { return p->MiddleName; } // Получение значения 2го узла списка
    void setValue(Node *p, int val) { p->FirstName = val; } // Установка значения узла списка
    Node* getFirst() { return head; } // Получение корневого узла списка
    Node* getLast();            // Получение последнего узла списка
    void Clear();               // Очистка списка
    Node* Next(Node *);         // Переход к следующему узлу
    Node* Add(string, /*string, string,*/  Node*); // Добавление узла списка
    Node* Delete(Node*);        // Удаление узла списка
    void Print();               // Вывод значений узлов списка
    void Swap(Node*, Node*);    // Взаимообмен двух узлов

    Node* Nomer_s_kontsa_del(); // удален середина по номеру
    Node* Zamena(); // замена
    Node* Zamena_ptr(); // замена по указателю
    Node* HeadToEnd(); // замена местами по указателю первый назад последний вперед
    Node* FILO(); // первый назад
    Node* LIFO(); // последний вперед
    void StekOperation(); // DZ po AIP

    Node* Dobav_n_last(string); // добавить в конец
    Node* Dobav_pre_last(); // добавить перед конец
    Node* Dobav_head(string); // добавить перед конец
    Node* Dobav_head_next(); // добавить перед конец

    Node* head_del(); // udalit golovu
    Node* head_next_del(); // udalit 2 s golovu
    Node* Delete_end(); // удаляет конец
    Node* Delete_prev_end(); // удален предпоследний

    Node* By_value_del(); // udalit po znacheniu
};

Node* List::Add(string num,// string num2, string num3,
    Node* node = NULL)
{
    Node *elem = new Node();
    elem->FirstName = num;
    //elem->LastName = num2;
    //->MiddleName = num3;
    count++;
    if (node == NULL) // Добавление нового корня
    {
        if (head == NULL) {
            elem->ptr = NULL;
            head = elem;
        }
        else {
            elem->ptr = head;
            head = elem;
        }
        return elem;
    }
    elem->ptr = node->ptr; // Добавление узла после текущего
    node->ptr = elem;
    return elem;
}

Node* List::Delete(Node* node)
{
    if (node == NULL) { return NULL; } // В списке нет узлов
    count--;
    if (node == head)   // Удаление корневого узла
    {
        head = node->ptr;
        delete node;
        return head;
    }
    Node* prev = Prev(node); // Удаление промежуточного узла
    prev->ptr = node->ptr;
    delete node;
    return prev;
}
////////////////
Node* List::Delete_end()
{
    Node *temp = NULL;
    Node *head2 = head;
    if (head2 == NULL) { return NULL; } // В списке нет узлов
    count--;
    while (head2->ptr != NULL) {  // перемотка на последние указатели
        temp = head2;
        head2 = head2->ptr;
    }
    if (temp) {
        //<udalenie poslednego>
        temp->ptr = NULL;
        delete head2;
        //< /udalenie poslednego>
    }
    cout << temp->FirstName  <<" - " << temp << " - " << temp->ptr << endl;
}
////////////////
////////////////
Node* List::Dobav_head(string value = "ADD-TEST")
{
    Node *temp = NULL;
    Node *head2 = head;
    //Node *uzel = head;
    //cout << "add to head: ";
    cin >> value;
    //<opation>
    Node *elem2 = new Node();
    elem2->FirstName = value;
    elem2->ptr = head2;
    head = elem2;
    //</opation>
    if (head2 == NULL) { return NULL; } // В списке нет узлов
    count++;
}
////////////////
////////////////
Node* List::Dobav_head_next()
{
    Node *t1 = NULL;
    Node *t2 = head;
    t1 = head;
    t2 = t2->ptr;
    //<operation>
    Node *elem2 = new Node();
    elem2->FirstName = "88";
    t1->ptr = elem2;
    elem2->ptr = t2;
    //<operation>
    if (t2 == NULL) { return NULL; } // В списке нет узлов
    count++;
}
////////////////
////////////////
Node* List::Dobav_n_last(string value = "88")
{
    Node *temp = NULL;
    Node *head2 = head;
    if (head2 == NULL) { return NULL; } // В списке нет узлов
    count++;
    while (head2->ptr != NULL) {
        temp = head2;
        head2 = head2->ptr;
    }
    // <operation>
    Node *elem2 = new Node();
    elem2->FirstName = value;
    elem2->ptr = NULL;
    head2->ptr = elem2;
    // </operation>
    cout << head2->FirstName << " test " << head2 << " test " << endl;
    cout << head2->ptr->FirstName << " test " << head2->ptr << " test " << endl;
}
////////////////
/////////////////
Node* List::Dobav_pre_last()
{
    Node *temp = NULL;
    Node *t = head;
    Node *head2 = head;
    if (head2 == NULL) { return NULL; } // В списке нет узлов
    count--;
    while (head2->ptr != NULL) {
    head2 = head2->ptr;
    t = t->ptr;
        if (t->ptr->ptr == NULL) {
        temp = t->ptr;
        cout << t->FirstName << " test2 " << t << " test2 " << endl;
        cout << temp->FirstName << " test2 " << temp->ptr << " test2 " << endl;
        //<operation>
        Node *elem2 = new Node();
        elem2->FirstName = 88;
        t->ptr = elem2;
        elem2->ptr = temp;
        //</operation>
        return NULL;
        }
    }
}
////////////////
////////////////
Node* List::Delete_prev_end()
{
    count++;
    Node *temp = NULL;
    Node *head2 = head;
    Node *t = head;
    Node *t2 = head;
    Node *t3 = head;
    if (head2 == NULL) { return NULL; } // В списке нет узлов
    if (head2->ptr == NULL) { return NULL; } // В списке нет узлов по условию
    if (head2->ptr->ptr == NULL) { return NULL; } // В списке нет узлов
    count--;
    int j = 0;
    cout << head2->FirstName << " - " << head2 << " - " << endl;
    while (head2->ptr != NULL) {j++;
                head2 = head2->ptr;
                temp = head2;
                t = temp->ptr;
                t3 = t->ptr;
        cout << temp->FirstName << " - " << temp << " - " << endl;
        cout << t->FirstName << " - " << t << " - " << endl;
        cout << t3->FirstName << " - " << t3 << " - " << endl;

        if (head2->ptr->ptr->ptr == NULL) {
            //// <operation>
            temp->ptr = t3; delete t;
            //// </operation>
            cout << temp->FirstName << " Проверка " << temp << " - " << endl;
            cout << temp->ptr->FirstName << " Проверка " << temp->ptr << " - " << endl;
            cout << "temp->ptr->ptr->FirstName" << " Проверка " << temp->ptr->ptr << " - " << endl;
            cout << "t3->ptr->FirstName" << " - " << t3->ptr << " - " << endl;
            return NULL;
        }
    }
}
///////////////////
////////////////
Node* List::Nomer_s_kontsa_del()
{
    count++;
    Node *temp = NULL;
    Node *head2 = head;
    Node *t = head;
    Node *t2 = head;
    Node *t3 = head;
    Node *t4 = head;
    int nomer_s_kontsa = 4;
    if (head2 == NULL) { return NULL;  } // В списке нет узлов
    count--;
    int i = 0;
    int vsego;
    while (t2->ptr != NULL) {
        t2 = t2->ptr;
        i++;
        vsego = i;
    }
    // proverka na sootvetstvie spisku
    if ((vsego+1) <= nomer_s_kontsa) { cout << " Nomer ne sootvetstvuet spisku|" << nomer_s_kontsa << "- этого номера нет " << endl;   return NULL; }

    cout << " vsego  " << (vsego+1) << " - " << endl;
    int j = 0;

    while (head2->ptr != NULL) {
        if (j == (vsego - nomer_s_kontsa)) {
                temp = head2;
                t = temp ->ptr;
                t3 = t->ptr;
                //// <perenos ukazatelya udalenie>
                temp->ptr = t3; delete t;
                //// </ perenos ukazatelya udalenie>
                cout << j << " Проверка " << temp << " - " << endl;
                head2 = head2->ptr;
        }
        else {
            head2 = head2->ptr;
        }
        j++;
    }
}
///////////////////
////////////////
Node* List::By_value_del()
{
    Node *temp = NULL;
    Node *head2 = head;
    Node *t = head;
    Node *t2 = head;
    Node *t3 = head;
    Node *t4 = head;
    string value_del = "31";
    if (head2 == NULL) { return NULL; } // В списке нет узлов
    count--;
    int j = 0;
    while (head2->ptr != NULL) {
        temp = head2;
        head2 = head2->ptr;
        if (head2->FirstName == value_del) {
            t = temp->ptr;
            t3 = t->ptr;
            //// <operation>
            temp->ptr = t3; delete t;
            //// </operation>
            cout << j << " Проверка " << temp << " - " << endl;
            break;
        }
        else {
        }
        j++;
    }
}
///////////////////
////////////////
Node* List::head_next_del()
{
    Node *t1 = NULL;
    Node *head2 = head;
    Node *t2 = head;
    Node *t3 = head;
    t1 = head;
    t2 = t1->ptr;
    t3 = t2->ptr;
    if (head2 == NULL) { return NULL; } // В списке нет узлов
    // <ukazateli dlya operatsii>
    cout << t1->FirstName << " - " << t1 << " - " << endl;
    cout << t2->FirstName << " - " << t2 << " - " << endl;
    cout << t3->FirstName << " - " << t3 << " - " << endl;
    // </ukazateli dlya operatsii>
    // <operation>
    t1->ptr = t3;
    t2->ptr = NULL;
    delete t2;
    // </operation>
    // <proverka>
    cout << head2->FirstName << " - " << head2 << " - " << endl;
    cout << head2->ptr->FirstName << " - " << head2->ptr << " - " << endl;
    cout << head2->ptr->ptr->FirstName << " - " << head2->ptr->ptr << " - " << endl;
    // </proverka>
}
////////////////
////////////////
Node* List::head_del()
{
    Node *temp = NULL;
    Node *head2 = head;
    Node *t = head;
    if (head2 == NULL) { return NULL; } // В списке нет узлов
    //<operation>
    head = head2->ptr;
    t = NULL;
    delete t;
    //</operation>
    int i = 0;
    while (head2->ptr != NULL) {
        temp = head2;
        head2 = head2->ptr;
        cout << i << " t " << t << " t " << endl;
        cout << i << " - " << temp << " - " << endl;
        cout << i << " - " << head2->ptr << " - " << endl;
        i++;
    }
}
////////////////
////////////////
Node* List::Zamena_ptr()
{
    Node *temp = NULL;
    Node *head2 = head;
    Node *t = head;
    Node *t2 = head;
    Node *t3 = head;
    Node *t4 = head;
    if (head2 == NULL) { return NULL; } // В списке нет узлов
    int i = 0;
    int n_zameny=5;
        while (head2->ptr != NULL) {
        t2 = head2;
        head2 = head2->ptr;
        if (i == (n_zameny-2)) {
            temp = head2;
            cout << " Замена " << n_zameny << endl;
            head2 = head2->ptr;
            t3 = temp->ptr;
            // <vivod nuzhnih peremennih>
            cout << t->FirstName << " - " << t << " - " << endl;
            cout << t2->FirstName << " - " << t2 << " - " << endl;
            cout << temp->FirstName << " - " << temp << " - " << endl;
            cout << t3->FirstName << " - " << t3 << " - " << endl;
            // </vivod nuzhnih peremennih>
            // </ podstanovka>
             t4 = t4->ptr;
             t2->ptr = t; t->ptr = t3;
             head = temp;
             temp->ptr = t4;
             // < podstanovka>
             // < proverka>
            cout << head->FirstName << " 1 " << head << " - " << endl;
            cout << t2->FirstName << " n " << t2 << " - " << endl;
            cout << t2->ptr->FirstName << " n+1 " << t2->ptr << " - " << endl;
            cout << t3->FirstName << " n+2 " << t3 << " - " << endl;
            // < proverka>
        }
        i++;
    }
}
///////////////////
////////////////
Node* List::HeadToEnd()
{
    Node *temp = NULL;
    Node *head2 = head;
    Node *t = head;
    Node *t2 = head;
    Node *t3 = head;
    Node *t4 = head;
    if (head2 == NULL) { return NULL; } // В списке нет узлов
    int i = 0;
    int n_zameny = 10;
    while (head2->ptr != NULL) {
        head2 = head2->ptr;
        t2 = head2;
        if (t2->ptr->ptr->ptr == NULL) {
            t2 = head2;
            temp = t2->ptr;
            cout << " Замена " << n_zameny << endl;
            //head2 = head2->ptr;
            t3 = temp->ptr;
            // <vivod nuzhnih peremennih>
            cout << t->FirstName << " - " << t << " - " << endl;
            cout << t2->FirstName << " - " << t2 << " - " << endl;
            cout << temp->FirstName << " - " << temp << " - " << endl;
            cout << t3->FirstName << " - " << t3 << " - " << endl;
            // </vivod nuzhnih peremennih>
            // </ podstanovka>
            t4 = t4->ptr;
            head = t3;
            t3->ptr = t4;
            temp->ptr = t; t->ptr = NULL;
            // < podstanovka>
            return NULL;
        }
        i++;
    }
}
///////////////////
////////////////
Node* List::LIFO()
{
    Node *temp = NULL;
    Node *head2 = head;
    Node *t = head;
    Node *tt = head;
    Node *t2 = head;
    Node *t3 = head;
    Node *t4 = head;
    if (head2 == NULL) { return NULL; } // В списке нет узлов
    int i = 0;
    int n_zameny = 10;

    while (head2->ptr != NULL) {
            t2 = head2;
            t4 = t2->ptr;

        if (t2->ptr->ptr == NULL) {
            // <vivod nuzhnih peremennih>
            cout << t2->FirstName << " -- " << t2 << " - " << endl;
            cout << t4->FirstName << " -- " << t4 << " - " << endl;
            // </vivod nuzhnih peremennih>
            // </ podstanovka>
            head = t4;
            t4->ptr = t3;
            t2->ptr = NULL;
            // < podstanovka>
            return NULL;
        }
        head2 = head2->ptr; t2 = t2->ptr;
        i++;
    }

}
///////////////////
////////////////
Node* List::FILO()
{
    Node *temp = NULL;
    Node *head2 = head;
    Node *t = head;
    Node *tt = head;
    Node *t2 = head;
    Node *t3 = head;
    Node *t4 = head;
    if (head2 == NULL) { return NULL; } // В списке нет узлов
    int i = 0;
    while (head2->ptr != NULL) {
        head2 = head2->ptr;
        t2 = head2;
        if (t2->ptr == NULL) {
            t2 = head2;
            temp = t2->ptr;
            // <vivod nuzhnih peremennih>
            //cout << t->FirstName << " -- " << t << " - " << endl;
            //cout << t2->FirstName << " -- " << t2 << " - " << endl;
            // </vivod nuzhnih peremennih>
            // </ podstanovka>
            t4 = t4->ptr;
            head = t4;
            t2->ptr = t;
            t->ptr = NULL;
            // < podstanovka>
            return NULL;
        }
        i++;
    }

}
///////////////////
////////////////
Node* List::Zamena()
{
    Node *temp = NULL;
    Node *head2 = head;
    Node *t = head;
    if (head2 == NULL) { return NULL; } // В списке нет узлов
    int i = 0;
    int n_zameny;
    cout <<  " Введи номер замены " << endl;
    cin >> n_zameny;

    while (head2->ptr != NULL) {
        if (i == (n_zameny-1)) {
            temp = head2;
            cout << " Замена " << n_zameny << endl;
        }
        head2 = head2->ptr;
        cout << i << " - " << t << " - " << endl;
        cout << i << " - " << temp << " - " << endl;
        cout << i << " - " << head2->ptr << " - " << endl;
        i++;
    }
    if (temp) {
        string zamen1;
        zamen1 = temp->FirstName;
        temp->FirstName = t->FirstName; // вставляем значение первого в выбранный
        t->FirstName = zamen1; // вставляем в первый значение выбранного
    }
}
///////////////////
////////////////
void List::StekOperation()
{
    while (true)
    {
        int day;
        cout << "Operation  Dobav_head-1 head_del-2 AddTail-3 DelTail-4 Print-5 Exit-6 \n";
        cin >> day;
        switch (day) {
        case 1:
            cout << "Dobav_head\n"; Dobav_head();
            break;
        case 2:
            cout << "head_del\n"; head_del();
            break;
        case 3:
            cout << "AddTail\n"; Dobav_head(); FILO();
            break;
        case 4:
            cout << "DelTail\n";  LIFO(); head_del();
            break;
        case 5:
            cout << "Print\n"; Print();
            break;
        case 6:
            cout << "Exit\n"; goto tryAgain;
            break;
        }

    }
tryAgain: // это лейбл
    exit;
}
///////////////////
void List::Print()
{
    if (isEmpty()) { cout << "Список пуст" << endl; return; }
    Node *p = head;
    do {
        cout<< "(" <<getValue(p)
        //  << " "<< getValue2(p)
        //  << " " << getValue3(p)
            << ")\n";
        p = Next(p);
    } while (p != NULL);
    cout << endl;
}

void List::Clear()
{
    class Node *p = head;
    if (p == NULL) return;
    do {
        Node *d = p;
        p = Next(p);
        delete d;
    } while (p != NULL);
    count = 0;
    head = NULL;
}

Node* List::getLast()
{
    Node* p = head;
    while (Next(p) != NULL)
        p = Next(p);
    return p;
}

Node* List::Next(Node* node)
{
    if (isEmpty()) return NULL;
    return node->ptr;
}

Node* List::Prev(Node* node)
{
    if (isEmpty()) return NULL;
    if (node == head) return NULL;
    Node *p = head;
    while (p->ptr != node)
        p = p->ptr;
    return p;
}

void List::Swap(Node* node1, Node* node2)
{
    if (node1 == NULL || node2 == NULL) return;
    if (node1 == node2) return;
    if (node2->ptr == node1)
    {
        Node *p = node1;
        node1 = node2;
        node2 = p;
    }
    Node *prev1 = Prev(node1);
    Node *prev2 = Prev(node2);
    Node *next1 = Next(node1);
    Node *next2 = Next(node2);
    if (next1 == node2)
    {
        if (prev1 != NULL)
            prev1->ptr = node2;
        else
            head = node2;
        node2->ptr = node1;
        node1->ptr = next2;
        return;
    }
    if (prev1 != NULL)
        prev1->ptr = node2;
    else
        head = node2;
    if (prev2 != NULL)
        prev2->ptr = node1;
    else
        head = node1;
    node2->ptr = next1;
    node1->ptr = next2;
}



int main()
{
    using std::string;
    using std::cin;
    using std::cout;
    using std::getline;
    system("chcp 1251");
    system("cls");
    List list;
    list.Print();
    Node *s = list.getLast();
    for (int i = 0; i < 4; i++) {
        string z;
        //string z2;
        //string z3;
        cout << ">> FirstName  ";
        cin >> z;
        //cout << ">> LastName  ";
        //cin >> z2;
        //cout << ">> MiddleName  ";
        //cin >> z3;
        s = list.Add(z, //z2, z3,
            s);
    }
    //list.Delete_end();
    //list.Nomer_s_kontsa_del();
    //list.By_value_del();
    //list.Delete_prev_end();

    //list.Zamena();
    //list.Zamena_ptr();
    //list.head_next_del();
    //list.Dobav_n_last();
    //list.Dobav_pre_last();
    //list.StekOperation();



    //list.Dobav_head_next();
    //list.HeadToEnd();
list.FILO();
//list.LIFO();
    //cout << "***********************" << endl;
    //list.Print();
    //cout << "Последний элемент: " << list.getValue(list.getLast()) << endl;
    // Удаляем элементы, равные 0
    //Node *p = list.getFirst();
    //do {
    //  if (list.getValue(p) == "0")
    //      p = list.Delete(p);
    //  else
    //      p = list.Next(p);
    //} while (p != NULL);
    //list.Print();
    //cout << "В списке " << list.getCount() << " элементов" << endl;
    //list.Swap(list.getFirst(), list.getLast());
    list.Print();
    //list.Clear();
    //list.Print();
    //cout << "В списке " << list.getCount() << " элементов" << endl;
    //cin.get(); cin.get();

    return 0;

}