Добавление элемента в список

#define _CRT_SEcurrentE_NO_WARNINGS

#include <iostream>
#include <conio.h>
#include <stdio.h>
#include <string>
#include <Windows.h>
using namespace std;
#define QUEUE struct gorod

QUEUE
{
int num, year;
string fio,adres;

QUEUE* next;
QUEUE* prev;
};

QUEUE* head = NULL;
QUEUE* last = NULL;
QUEUE* current = NULL;
QUEUE* temp = NULL;
QUEUE* newList = NULL;

void add_name(int num, int year, string fio, string adres)
{
if (head != NULL)
{
newList = new QUEUE;
newList->num = num;
newList->year = year;
newList->fio = fio;
newList->adres = adres;
newList->next = NULL;
newList->prev = current;
current->next = newList;
last = newList;
current = newList;
}
else
{
newList = new QUEUE;
newList->num = num;
newList->year = year;
newList->fio = fio;
newList->adres = adres;

head = newList;
newList->next = NULL;
newList->prev = NULL;
current = newList;
last = head;
}
}
void delete_unit(int num)
{
newList = head;
while (newList) {
if (newList->num == num)
{
if (newList == head) {
head = head->next;
if (head)
head->prev = NULL;
else
last = NULL;
if (current == newList)
current = head;
delete newList;
cout << "Complete!" << endl;
_getch();
break;
}
if (newList == last) {
last = last->prev;
if (last)
last->next = NULL;
if (current == newList)
current = last;
delete newList;
cout << "Complete!" << endl;
_getch();
break;
}
else {
cout << "Not find!" << endl;
_getch;
}
newList->prev->next = newList->next;
newList->next->prev = newList->prev;
current = newList->prev;
delete newList;
break;
}
newList = newList->next;
}
}
void sort()
{
gorod* cur = head;
while (cur->next)
{
if ((cur->num) > (cur->next->num)) {
cur = cur->next;
sort();
}
}
}
void show_list(gorod* head)
{

QUEUE* curr = nullptr, * prev = nullptr;
gorod* p = head;
while (p)
{
cout << endl;
cout << "----------------------------------" << endl;

cout << "Год рождения: " << p->year << endl;
cout << "Адрес: " << p->adres << endl;
cout << "ФИО: " << p->fio << endl;
p = p->next;
}
}
void show_list_n(int num)
{
gorod* info = head;
while (info)
{
if (info->num == num)
{
cout << "----------------------------------" << endl;
cout << "----------------------------------" << endl;

cout << "Год рождения: " << info->year << endl;
cout << "Адрес: " << info->adres << endl;
cout << "ФИО: " << info->fio << endl;
}
info = info->next;
}
cout << "\n";
}

int main() {
SetConsoleCP(1251);
SetConsoleOutputCP(1251);
int enter_num, num, key, n = 0, year, year_fin;
string fio, adres;


while (true)
{
system("cls");
cout << "1. Ввести данные\n";
cout << "2. Удаление элемента по номеру\n";
cout << "3. Вывод всего списка\n";
cout << "4. Вывод по заданному номеру\n";
cout << "5. Возраст\n";
cout << "6. Выход\n";
key = _getch();
switch (key)
{
case '1':
{
system("cls");
cout << "Введите номер горожанина: ";
cin >> enter_num;
cout << "Введите ФИО: ";
cin >> fio;
cout << "Введите год Рождения: ";
cin >> year;
cout << "Введите адрес: ";
cin >> adres;
add_name(enter_num,year,fio,adres);
n++;
if (n == 0) {
}
else if (n > 0) {
sort();
}
break;
}
case '2':
{
system("cls");
cout << "Введите номер для удаления: ";
cin >> enter_num;
delete_unit(enter_num);
if (n <= 0)
n = 0;
else
n--;

break;
}
case '3':
{
system("cls");
cout << "------ Заявки ------" << endl;
show_list(head);
_getch();
break;
}
case '4':
{
cout << "Введите номер для поиска: ";
cin >> num;
system("cls");
cout << "------ Заявки по номеру " << num << " -----" << endl;
show_list_n(num);
_getch();
break;
}
case '5':
{
cout << "Введите номер для поиска: ";
cin >> num;
system("cls");
cout << "Возраст горожанина под номером " << num << " = "<< 2020-year << endl;
cin >> year_fin;
}
case '6':
{
exit(0);
break;
}
default:
{
cout << "Error\n";
_getch();
break;
}
if (key == 0) break;
}
}
return 0;
}