I have a base class Participant and I need to sort object in array of participant by quantity of their prizes or diplomas. The virtual function get_data return this number. But whileI try to sort, i've got error Access violation executing in row with comparing 2 numbers. if (p[j].Get_Data() < p[i].Get_Data()) { This is my full code:

#include <iostream>
#include <string>
#include <vector>
using namespace std;

class Participant {
protected:
    string name;
    string surname;
    vector <string> type;
    int age;
public:
    Participant() : name(""), surname(""), type(), age(0)
    {}
    Participant(string name, string surname, vector <string> type, int age) {
        this->name = name;
        this->surname = surname;
        this->type = type;
        this->age = age;
    };
    Participant(const Participant& other) : name(other.name), surname(other.surname), type(other.type), age(other.age)
    {
    }
    Participant& operator=(const Participant& other)
    {
        name = other.name;
        surname = other.surname;
        type = other.type;
        age = other.age;
        return *this;
    }
    virtual int Get_Data() {
        return 0;
    }
    friend void Sort(Participant* p);
};

class Diploma : public Participant {
protected:
    vector<int> places;
    vector <string> type_d;
public:
    Diploma() : places(), type_d{}
    {}
    Diploma(string name, string surname, vector <string> type, int age, vector<int> places, vector <string> type_d);
    int Get_Data() override {
        cout << "diplom prize" << endl;
        cout << type_d.size() << endl;
        return type_d.size();
    }
};
class Prize : public Participant {
protected:
    vector <int> places;
    vector<string> prize;
public:
    
    Prize(string name, string surname, vector <string> type, int age, vector<int> places, vector<string> prize);
    int Get_Data() override{
        cout << "Cont prize" << endl;
        cout << prize.size() << endl;
        return prize.size();
    }
};
Prize::Prize(string name, string surname, vector <string> type, int age, vector<int> places, vector<string> prize) {
    this->name = name;
    this->surname = surname;
    this->type = type;
    this->age = age;
    this->places = places;
    this->prize = prize;
}
Diploma::Diploma(string name, string surname, vector <string> type, int age, vector<int> places, vector <string> type_d){
    this->name = name;
    this->surname = surname;
    this->type = type;
    this->age = age;
    this->places = places;
    this->type_d = type_d;

}
void Sort(Participant* p) {
    Participant temp;
    for (int i = 0; i < 3; i  ) {
        for (int j = i   1; j < 3; j  )
        {
            if (p[j].Get_Data() < p[i].Get_Data()) {
                temp = p[i];
                p[i] = p[j];
                p[j] = temp;
            }
        }

    }
}

int main() {
    Participant* pa[3];
    pa[0] = new Diploma("Alex", "Smith", { "Geo","Math" }, 17, { 1,6 }, { "first"});
    pa[1] = new Prize("Helen", "Blink", { "IT","Math" }, 18, { 2,2 }, {"Golden medal", "medal"});
    pa[2] = new Prize("Brandon", "Brown", { "IT","Math" }, 18, { 2,2 }, { "Golden medal", "medal","gold"});
    Sort(*pa);
    for (int i = 0; i < 3; i  ) {
        pa[i]->Get_Data();
        cout << endl;
    }
}

CodePudding user response：

The issue here is that when you are passing *pa, only the first element is accessible. If you run it in debug mode you will be able to see that inside sort function, p[1] is not a valid object. Basically, only p[0] is passed to the function. You should pass the reference to the array i.e. **pa to the sort function

void Sort(Participant **p)
{
    Participant *temp;
    for (int i = 0; i < 3; i  )
    {
        for (int j = i   1; j < 3; j  )
        {
            if (p[j]->Get_Data() < p[i]->Get_Data())
            {
                temp = p[i];
                p[i] = p[j];
                p[j] = temp;
            }
        }
    }
}

int main()
{
    Participant *pa[3];
    pa[0] = new Diploma("Alex", "Smith", {"Geo", "Math"}, 17, {1, 6}, {"first"});
    pa[1] = new Prize("Helen", "Blink", {"IT", "Math"}, 18, {2, 2}, {"Golden medal", "medal"});
    pa[2] = new Prize("Brandon", "Brown", {"IT", "Math"}, 18, {2, 2}, {"Golden medal", "medal", "gold"});
    Sort(pa);
    for (int i = 0; i < 3; i  )
    {
        pa[i]->Get_Data();
        cout << endl;
    }
}