Question

I have this code. From main function i twice call sportPrisevinners function and if it is first call of this function it works correctly and I recive correct result, but when i call it second time I recive incorrect result even I pass this function with same arguments. Please help me to solve this problem while it doesn`t make me crasy.

const char* countries[] = {"ru", "gb", "us", "uk", "ch", "de"};
const int countriesCount = 6;
const char* sports[] = {"runing", "swiming", "baseball", "football", "jumping", "kerling"};
const int sportsCount = 6;

enum {
    Empty = 0,
    Bronse,
    Silver,
    Gold
};

struct member {
    char sport[9];
    char country[3];
    int points;
    int medal;
};

struct members {
    member* list;
    int count;
};

string medalToStr(int medal)
{
    switch (medal) {
    case Gold:
        return "Gold";
    case Silver:
        return "Silver";
    case Bronse:
        return "Bronse";
    default:
        return "Empty";
    }
}

void printMembers(members &list)
{
    for (int i = 0; i < list.count ; i++)
        cout << /*i << " " <<*/ medalToStr(list.list[i].medal) << " in "
             << list.list[i].sport << " with " << list.list[i].points
             << " from " << list.list[i].country << endl;
}

void generate()
{
    ofstream file("members.dat", ios::binary|ios::trunc);

    member temp;

    for (int i = 0; i < sportsCount ; i++)
        for (int j = 0; j < countriesCount ; j++)
        {
            int count = rand()%5+5;
            for (int k = 0; k < count ; k++)
            {
                strcpy(&temp.sport[0], sports[i]);
                strcpy(&temp.country[0], countries[j]);
                temp.points = rand()%100;
                temp.medal = Empty;

                file.write((char*)&temp, sizeof(member));
            }
        }

    file.close();
}

members sportPrisevinners(const char* sport)
{
    //reading
    ifstream file("members.dat", ios::binary);
    member* loaded = new member[60];
    int pos = 0;
    while (!file.eof())
    {
        member temp;

        file.read((char*)&temp, sizeof(member));

        static bool reading = false;
        if (strncmp(&temp.sport[0], sport, strlen(sport))==0) {
            reading = true;
            loaded[pos++] = temp;
        } else if (reading) {
            break;
        }
    }
    file.close();

    //sorting
    int count = 3;
    for (int i = 0; i < pos-1 ; i++)
    {
        for (int j = i+1; j < pos ; j++)
            if (loaded[i].points<loaded[j].points)
            {
                member temp = loaded[i];
                loaded[i] = loaded[j];
                loaded[j] = temp;
            }

        if (i<count) {
            static int last = -1;

            if (loaded[i].points==last)
                count++;

            loaded[i].medal = count-i;
            last = loaded[i].points;
        } else break;
    }

    //returning
    members result;

    result.list = new member[count];
    memcpy(result.list, loaded, count*sizeof(member));
    /*for (int i = 0; i < count; i++)
        result.list[i] = loaded[i];*/
    result.count = count;

    delete[] loaded;

    return result;
}

int main(int /*argc*/, char */*argv*/[])
{
    srand(time(0));

    generate();

    members r = sportPrisevinners(sports[4]);
    printMembers(r);
    delete[] r.list;
    members l = sportPrisevinners(sports[5]);
    printMembers(l);
    delete[] l.list;

    system("pause");

    return 0;
}

Answer 1

I suspect it’s the static local variables in your function. They won’t have the same values on each call to the function, and this could affect the results. The initialization of these variables is performed just once – the first time they come into scope – so each subsequent time the function is called, you pick up the values these variables had last time the function ran.