对指针向量进行排序后，一旦工作便崩溃，并显示“无法读取内存”

Question

I have a vector of Flight pointers that I pass into a function to be sorted and displayed on the screen. I am using a functor in the Flight class to do the sorting. It works perfectly the first time, then after the sortCriteria is incremented, it crashes when it tries to step through the flights vector the second time. The error I get says Access violation reading location 0x013DFFFC , so I'm betting it's got something to do with loosing track of the memory location of the vector after it gets sorted the first time. Thanks in advance for any help you can offer. Here is my sorting function:

//this function displays the flight schedule and sorts it by any field
void showFlightSchedule(vector<Flight*>& flights)
{
    //declare local variables
    char choice = ' ';
    int sortCriteria = 1;
while (toupper(choice) != 'X')
{
    //choosing which field to sort the schedule by
    switch (sortCriteria)
    {
    case 1:
        sort (flights.begin(), flights.end(), Flight::SortByDepartCity);
        break;
    case 2:
        sort (flights.begin(), flights.end(), Flight::SortByDestinationCity);
        break;
    case 3:
        sort (flights.begin(), flights.end(), Flight::SortByDepartTime);
        break;
    case 4:
        sort (flights.begin(), flights.end(), Flight::SortByArrivalTime);
        break;
    case 5:
        sort (flights.begin(), flights.end(), Flight::SortByFlightNumber);
        break;
    case 6:
        sort (flights.begin(), flights.end(), Flight::SortByAircraftType);
        break;
    case 7:
        sort (flights.begin(), flights.end(), Flight::SortByFreqFlyPoints);
        break;
    case 8:
        sort (flights.begin(), flights.end(), Flight::SortByFlightFull);
        break;
    }


    //display header
    system("cls");
    cout << left << endl;
    cout << "     " << setw(7) << "From" << setw(6) << "To" << setw(8) << "Depart" << setw(8) << "Arrive" <<
        setw(8) << "Flight" << setw(12) << "Aircraft" << setw(12) << "Frequent" << setw(6) << "Flight\n";
    cout << "\t\t\t\t  " << setw(10) << "Number" << setw(8) << "Type" << setw(14) << "Flyer Points" << setw(6) << "Status\n";

    //slightly altering the header to indicate how the list is sorted
    switch (sortCriteria)
    {
    case 1:
        cout << "   --\\_/------------------------------------------------------------------\n\n";
        break;
    case 2:
        cout << "   ---------\\_/-----------------------------------------------------------\n\n";
        break;
    case 3:
        cout << "   ----------------\\_/----------------------------------------------------\n\n";
        break;
    case 4:
        cout << "   ------------------------\\_/--------------------------------------------\n\n";
        break;
    case 5:
        cout << "   --------------------------------\\_/------------------------------------\n\n";
        break;
    case 6:
        cout << "   -----------------------------------------\\_/---------------------------\n\n";
        break;
    case 7:
        cout << "   -----------------------------------------------------\\_/---------------\n\n";
        break;
    case 8:
        cout << "   ----------------------------------------------------------------\\_/----\n\n";
        break;
    }

    //step through the flights vector displaying the information
    for (int idx = 0; idx < flights.size(); idx++)
    {
        cout << "     " << setw(7) << flights[idx]->getDepartCity() << setw(6) << flights[idx]->getDestinationCity() << setw(8) <<
            flights[idx]->getDepartTime() << setw(9) << flights[idx]->getArrivalTime() << setw(10) << flights[idx]->getFlightNumber() << setw(11) <<
            flights[idx]->getAircraftType() << setw(11) << flights[idx]->getFreqFlyPoints();
        if (flights[idx]->getFlightFull())
            cout << setw(6) << "FULL\n\n";
        else
            cout << endl << endl;
        flights[idx]++;
    }

    //display footer
    cout << "   -----------------------------------------------------------------------\n\n";
    cout << "\t\t\t  C -- Change Sorting\n";
    cout << "\t\t\t  X -- Exit to Main Menu\n";
    cout << "\t\t\t  Enter C or X: ";

    //get choice from user
    cin >> choice;

    //error-trapping loop
    while ((toupper(choice) != 'C') && (toupper(choice) != 'X'))
    {
        cout << "Please choose \"C\" or \"X\": ";
        cin >> choice;
    }

    //changing the sort flag
    if (sortCriteria == 8)
        sortCriteria = 1;
    else
        sortCriteria++;     
}

}

And in my Flight.h file, I have these sort statements:

static bool SortByDepartCity(const Flight* f1, const Flight* f2)
{
    return f1->departCity < f2->departCity;
}

static bool SortByDestinationCity(const Flight* f1, const Flight* f2)
{
    return f1->destinationCity < f2->destinationCity;
}

static bool SortByDepartTime(const Flight* f1, const Flight* f2)
{
    return f1->departTime < f2->departTime;
}

static bool SortByArrivalTime(const Flight* f1, const Flight* f2)
{
    return f1->arrivalTime < f2->arrivalTime;
}

static bool SortByFlightNumber(const Flight* f1, const Flight* f2)
{
    return atoi(f1->flightNumber.c_str()) < atoi(f2->flightNumber.c_str());
}

static bool SortByAircraftType(const Flight* f1, const Flight* f2)
{
    return f1->aircraftType < f2->aircraftType;
}

static bool SortByFreqFlyPoints(const Flight* f1, const Flight* f2)
{
    return f1->freqFlyPoints > f2->freqFlyPoints;
}

static bool SortByFlightFull(const Flight* f1, const Flight* f2)
{
    return f1->flightFull < f2->flightFull;
}

Answer 1

remove this

flights[idx]++;

at the last line of printing loop.

PS Here's some code to simplify yours

template< class T, class FieldType, FieldType T::*FieldPtr >
struct LessBy {
    bool operator()( const T * left, const T * right ) const {
        return left->*FieldPtr < right->*FieldPtr;
    }
};

typedef LessBy< Flight, std::string, & Flight::departCity > SortByDepartCity;
typedef LessBy< Flight, std::string, & Flight::destinationCity > SortByDestinationCity;
//and so on

Answer 2

This line that you do while printing:

flights[idx]++;

will modify every pointer, almost certainly making each and every one invalid to dereference.
You should remove it. (It looks like a line left over from older code.)

It would also be a good idea to separate sorting from printing, as nobody expects an output function to modify the data it's printing.

And unless you have a very good reason, you shouldn't be working with pointers to flights, anyway.