How to change and delete a variable in stack?

Question

1. Create a record to store the following information:
   • owner code
   • car number,
   • car model,
   • Release date,
   • date of registration.
2. Provide the ability to add, modify and delete records and displays data to the screen. Use the stack to store data.
3. Get a list of license plates and car brands registered in November and December last year.
4. Find the average age for each of the encountered car brands.
5. Find the "age" up to the year of each of the cars registered in February and March of the current year.

It is necessary that the record I need is deleted and edited (second, fifth, etc.). But it happens to only with the last record added. How to fix it?

#include <iostream>
#include <string>

using namespace std;

struct DATE
{
    int number;
    int month;
    int year;
};
struct informations
{
    char code[10];
    char number_car[10];
    char mark[10];
    DATE release;
    DATE registration;
    informations* next;  

} typedef Informations;

Informations* top = nullptr; 

void push()
{
    Informations* ptr = new Informations;  

    cin.get();
    cout << "Enter the code owner: ";
    cin.getline(ptr->code, 10); 
    cout << "Enter the number of the car: ";
    cin.getline(ptr->number_car, 10);
    cout << "Enter the mark of the car: ";
    cin.getline(ptr->mark, 10);

    cout << "Enter the date of release: " << endl;
    do {
        cout << "number: ";
        cin >> ptr->release.number;
    } while ((ptr->release.number > 31) || (ptr->release.number <= 0));
    do {
        cout << "month: ";
        cin >> ptr->release.month;
    } while ((ptr->release.month > 12) || (ptr->release.month <= 0)); 
    do {
        cout << "year: ";
        cin >> ptr->release.year;
    } while ((ptr->release.year > 2019) || (ptr->release.year <= 1980));  

    cout << "Enter the date of registration: " << endl;
    do {
        cout << "number: ";
        cin >> ptr->registration.number;
    } while ((ptr->registration.number > 31) || (ptr->registration.number <= 0));
    do {
        cout << "month: ";
        cin >> ptr->registration.month;
    } while ((ptr->registration.month > 12) || (ptr->registration.month <= 0));
    do {
        cout << "year: ";
        cin >> ptr->registration.year;
    } while ((ptr->registration.year > 2019) || (ptr->registration.year <= 1980)); 
    cout << endl;

    ptr->next = top; 
    top = ptr; 
}

void change()
{
    cin.get();
    cout << "Enter the code owner: ";
    cin.getline(top->code, 10);
    cout << "Enter the number of the car: ";
    cin.getline(top->number_car, 10);
    cout << "Enter the mark of the car: ";
    cin.getline(top->mark, 10);

    cout << "Enter the date of release:" << endl;
    do {
        cout << "number: ";
        cin >> top->release.number;
    } while ((top->release.number > 31) || (top->release.number <= 0));
    do {
        cout << "month: ";
        cin >> top->release.month;
    } while ((top->release.month > 12) || (top->release.month <= 0));
    do {
        cout << "year: ";
        cin >> top->release.year;
    } while ((top->release.year > 2019) || (top->release.year <= 1980));

    cout << "Enter the date of registration: " << endl;
    do {
        cout << "number: ";
        cin >> top->registration.number;
    } while ((top->registration.number > 31) || (top->registration.number <= 0));
    do {
        cout << "month: ";
        cin >> top->registration.month;
    } while ((top->registration.month > 12) || (top->registration.month <= 0));
    do {
        cout << "year: ";
        cin >> top->registration.year;
    } while ((top->registration.year > 2019) || (top->registration.year <= 1980));
    cout << endl;
}


void pop() 
{
    auto bad = top;  
    top = top->next;
    delete bad;
}

void show_stack() 
{
    int i = 0;
    cout << endl;
    Informations* ptr = top;
    while (ptr != NULL)
    {
        i++;
        cout << "           " << i << endl;
        cout << "The code owner: " << ptr->code << endl;
        cout << "The number of the car: " << ptr->number_car << endl;
        cout << "The mark of the car: " << ptr->mark << endl;
        cout << "The date of release:\nnumber:\t\t\t\t" << ptr->release.number << endl;
        cout << "month:\t\t\t\t" << ptr->release.month << endl;                        
        cout << "year:\t\t\t\t" << ptr->release.year << endl;
        cout << endl;
        cout << "The date of registration:\nnumber:\t\t\t\t" << ptr->registration.number << endl;
        cout << "month:\t\t\t\t" << ptr->registration.month << endl;
        cout << "year:\t\t\t\t" << ptr->registration.year << endl;
        cout << endl;
        ptr = ptr->next;
    }
}

void November_and_December()  
{
    Informations* ptr = top;
    while (ptr != NULL)
    {
        if ((ptr->registration.month == 11) || (ptr->registration.month == 12))
        {
            if (ptr->registration.year == 2018)
            {
                cout << "The number of the car: " << ptr->number_car << endl;
                cout << "The mark of the car: " << ptr->mark << endl;
                cout << endl;
                ptr = ptr->next;
            }
        }
        else cout << endl;
    }
}

void Average_age()
{
    Informations* ptr = top;
    int i = 0;
    int averageyear = 0;
    while (ptr != NULL)
    {
        i++;
        averageyear += ptr->release.year;
        ptr = ptr->next;
    }
    double average = averageyear / i;
    cout << average << endl;

}

void February_and_March()   
{
    int vozrast;
    Informations* ptr = top;
    while (ptr != NULL)

    {
        if (((ptr->registration.month == 2) || (ptr->registration.month == 3)) && (ptr->registration.year == 2019)) 
        {
            vozrast = (ptr->registration.year) - (ptr->release.year); 

            if ((ptr->registration.month) < (ptr->release.month)) 
            {
                vozrast = vozrast - 1;
                cout << "Age of car: " << vozrast << endl;
                cout << "The mark of the car: " << ptr->mark << endl;
                cout << endl;
                ptr = ptr->next;
            }


            else if ((ptr->registration.month) == (ptr->release.month))
            {
                if ((ptr->registration.number) < (ptr->release.number))
                {
                    vozrast = vozrast - 1;
                    cout << "Age of car: " << vozrast << endl;
                    cout << "The mark of the car: " << ptr->mark << endl;
                    cout << endl;
                    ptr = ptr->next;
                }
                else
                {
                    cout << "Age of car: " << vozrast << endl;
                    cout << "The mark of the car: " << ptr->mark << endl;
                    cout << endl;
                    ptr = ptr->next;
                }
            }

        }
        else {
            cout << "Age of car: " << vozrast << endl;
            cout << "The mark of the car: " << ptr->mark << endl;
            cout << endl;
            ptr = ptr->next;
        }
    }
}


int main()
{
    int l;
    do
    {
        cout << "--------------------------------------";
        cout << endl;
        cout << " 1)Enter " << endl << " 2)Change " << endl << " 3)Delete " << endl << " 4)Show " << endl << " 5)November and December " << endl << " 6)Average age" << endl << " 7)February and March" << endl << " 8)Exit " << endl;
        cin >> l;
        switch (l)
        {
        case 1:push(); break;
        case 2: {
            if (top != NULL) change(); break;
        }
        case 3:
        {
            if (top != NULL) pop(); break;
        }
        case 4:   show_stack(); break;
        case 5:
        {
            if (top != NULL) November_and_December(); break;
        }

        case 6: if (top != NULL) Average_age(); break;

        case 7:
        {
            if (top != NULL) February_and_March(); break;
        }

        default:break;
        }
    } while (l != 8);
}

Answer 1

Since your collection of data is actually a linked-list which is being treated as a stack by only operating on the top (head) node, you can simply provide the code and number to identify a unique car in the list and delete that node from your list. Since both code and number members are held as type char *, you can use strcmp to compare the values. To locate and delete an individual node from the list you can use:

void del_car (const char *code, const char *number)
{
    Informations **ppn = &top,      /* pointer to pointer to top node */
                  *pn = top;        /* pointer to top node */

    while (pn) {                    /* iterate over each car */
        /* compare with code and number to delete */
        if (strcmp(pn->code, code) == 0 && strcmp(pn->number, number) == 0) {
            *ppn = pn->next;        /* set node at current address to next */
            delete pn;              /* delete current node */
            return;
        }
        ppn = &pn->next;            /* advances address of current to next */
        pn = pn->next;              /* advance current to next */
    }

    fputs ("car not found.\n", stderr);     /* warn if no match found */
}

However, the use of new/delete and basic types of char * instead of using the current STL std::vector and std::string, is about a decade or more out of date. (there is nothing wrong with knowing how to use new/delete and fundamental types -- there is a lot of legacy code out there, but for new code, you are much better off letting the containers manage the memory for you)

Give it a try and let me know if you have further questions. See Linus on Understand Pointers for understanding why it is advantageous to iterate using both a pointer to top (a pointer-to-pointer) and the pointer top to delete the node in the list.