Помогите исправить ошибки в программе

[rar14]

Вот прога работы с деком. Там есть меню с некоторыми операциями над деком. Она работает. Но есть кое-какие баги. Например, когда удаляешь все элементы в деке, то при попытке посмотреть содержимое дека прога умирает. Протестируйте у себя на компиляторе. Помогите исправить недочеты. Спасибо.

#include <iostream>
#include <conio.h>
using namespace std;
 
 
struct deque {
        char title[20];
        char author[20];
        int  year;
    deque *prev;
        deque *next;
};
 
deque* create_deque();
deque* push_left(deque* d);
deque* push_right(deque* d);
void is_clear(deque* d);
deque* delete_right_element(deque* d);
deque* empty_deque(deque* d);
void get_right_element(deque* d);
void print_deque(deque* d);
 
 
 
int main() {
 
        // Созданем дек с первым элементом
    deque* deq = create_deque();
 
        char key;
        bool flag = true;
 
BEGIN:
 
        cout << "Press key <1> to push element in left"     << "\n";
        cout << "Press key <2> to push element in right"    << "\n";
        cout << "Press key <3> to check out deque on empty" << "\n";
        cout << "Press key <4> to delete the right element" << "\n";
        cout << "Press key <5> to delete all elements"      << "\n";
        cout << "Press key <6> to get the right element"    << "\n";
        cout << "Press key <7> to print deque"              << "\n";
        cout << "Press key <8> to exit"                     << "\n\n\n";
 
        while (1 && flag) {
                key = getch(); 
                if (key >= 49 && key <= 56) break;
        }
 
    switch (key) {
            case 49: {
                        deq = push_left(deq);
                        break;
                }
            case 50: {
                        deq = push_right(deq);
                        break;
                }
            case 51: {
                        is_clear(deq);
                        break;
                }
            case 52: {
                        deq = delete_right_element(deq);
                        break;
                }
            case 53: {
                        deq = empty_deque(deq);
                        break;
                }
            case 54: {
                    get_right_element(deq);
                        break;
                }
            case 55: {
                    print_deque(deq);
                        break;
                }
            case 56: exit(0);
        }
 
        while (1) {
                key = getch(); 
                if (key >= 49 && key <= 56) { 
                        flag = false;
                        break;
                }
        }
 
        system("cls");
 
    goto BEGIN;
 
 
        return 0;
}

[rar14]

Функции расположены внизу (продолжение файла).

deque* create_deque() {
    deque* node = new (deque);
        strcpy((*node).title, "Yazik Ci++");
        strcpy((*node).author, "V.V. Podbelsky");
    (*node).year   = 2007;
    (*node).prev = NULL;
        (*node).next = NULL;
        return node;
} // END OF FUNCTION
 
deque* push_left(deque* d) {
    deque* node = new (deque);
        while ((*d).prev) d = (*d).prev;
        cout << "\t" << "PUSH  LEFT:" << "\n\n";
    cout << "\t" << "    Title:  "; cin >> (*node).title;
    cout << "\t" << "    Author: "; cin >> (*node).author;
        cout << "\t" << "    Year:   "; cin >> (*node).year;
        cout << "\n\t" << "    Data is brought";
    (*node).prev = NULL;
        (*node).next = d;
        (*d).prev = node;
        return node;
} // END OF FUNCTION
 
deque* push_right(deque* d) {
    deque* node = new (deque);
        while ((*d).next) d = (*d).next;
        cout << "\t" << "PUSH  RIGHT:" << "\n\n";
    cout << "\t" << "    Title:  "; cin >> (*node).title;
    cout << "\t" << "    Author: "; cin >> (*node).author;
        cout << "\t" << "    Year:   "; cin >> (*node).year;
        cout << "\n\t" << "    Data is brought";
    (*node).prev = d;
        (*node).next = NULL;
        (*d).next = node;
        return node;
} // END OF FUNCTION
 
void is_clear(deque* d) {
    if (!d) {
        cout << "\tTHE DEQUE IS EMPTY";
        }
        else {
        cout << "\tTHE DEQUE IS NOT EMPTY";
        }
} // END OF FUNCTION
 
deque* delete_right_element(deque* d) {
    while ((*d).next) d = (*d).next;
    deque* tmp = d;
        d = (*d).prev;
    (*d).next = NULL;
        delete tmp;
    cout << "\tTHE RIGHT ELEMENT IS DELETED";
        return d;
} // END OF FUNCTION
 
deque* empty_deque(deque* d) {
        while ((*d).next) d = (*d).next;
        while (d) {
        deque* tmp = d;
                d = (*d).prev;
                delete tmp;
        }
        cout << "\tALL ELEMENTS IN DEQUE IS DELETED";
    return d;
} // END OF FUNCTION
 
void get_right_element(deque* d) {
    while ((*d).next) d = (*d).next;
        cout << "\t" << "THE RIGHT ELEMENT:" << "\n\n";
    cout << "\t" << "    Title:  " << (*d).title  << "\n";
    cout << "\t" << "    Author: " << (*d).author << "\n";
        cout << "\t" << "    Year:   " << (*d).year   << "\n";
} // END OF FUNCTION
 
void print_deque(deque* d) {
    while ((*d).prev) d = (*d).prev;
        cout << "\t" << "PRINT DEQUE:" << "\n\n";
        int count = 1;
        do {
        cout << "\t" << count++ << " > " << "Title:  " << (*d).title  << "\n";
                cout << "\t" << "    Author: "   <<               (*d).author << "\n";
            cout << "\t" << "    Year:   "   <<               (*d).year   << "\n\n";
                d = (*d).next;
        } while (d);
} // END OF FUNCTION