There is a problem sorting the vector in the classes based on the variables in the class

Question

I put a custom class in a vector, and I want to sort it based on the size of the variables in the class.

using namespace std;
class Player {
    string name;   
    int score;          
    int id;             
    size_t num;         // Size of bytes obtained in the free store
    char* p;            // Start address of free memory
public:
    string getName() { return name; }
    int getScore() { return score; }
    size_t getNum() { return num; }
    ifstream& read(ifstream& in)
    {
        in.read((char*)this, sizeof(Player));
        p = new char[num];
        in.read((char*)p, num); // pointer p is not really used (just part of the problem)
        return in;
    }
    friend ostream& operator<<(ostream& out, const Player& Player)
    {
        out << "name:" << left << setw(15) << Player.name << ", "
            << "id:" << setw(10) << Player.id << ", "
            << "score:" << Player.score << ", "
            << "num:" << Player.num;
        return out;
    }
};

int main()
{
    std::ifstream infile("file", std::ifstream::binary);

    vector<Player> v;
    v.reserve(10);

    for (int i = 0; i < 10; i++) {
        v[i].read(infile);
    }


    for (int i = 0; i < 10; i++) {
        cout << v[i] << endl;    // before sort
    }

    cout << endl << endl;

    // sort sentence

    for (int i = 0; i < 10; i++) {
        cout << v[i] << endl;     // after sort
    }
}

First, I tried to sort by member 'num'. I tried it in a variety of ways.

   friend bool compare(Player& player1, Player& player2); // in class
};
static bool compare(Player& player1, Player& player2) 
{
    return player1.num < player2.num;
}

...
std::sort(v.begin(), v.end(),compare);

or

std::sort(v.begin(), v.end(),[](Player& a, Player& b) {return a.getNum() < b.getNum(); });

or

    bool operator<(const Player& py)
    {
        return num < py.num;
    }
    bool operator>(const Player& py)
    {
        return num > py.num;
    }                           
    // in class
};
std::sort(v.begin(), v.end(), [](Player& a, Player& b) {return a < b; });

result what I wanted

before

name:jhxubuhgldh    , id:476109 , score:435832437, num:969
name:pmemwohbgqwwg  , id:789387 , score:257570203, num:481
name:zzirtu         , id:1477302, score:172025616, num:37
name:nxkrhdujq      , id:4481   , score:461657936, num:258
name:benijj         , id:1867600, score:39352766, num:658
name:wvukciloi      , id:734835 , score:416874932, num:605
name:fisp           , id:1611284, score:194548462, num:734
name:xfjvbgocgnvgfr , id:995733 , score:181002072, num:834
name:rmg            , id:911109 , score:153943559, num:415

after

name:zzirtu         , id:1477302, score:172025616, num:37
name:nxkrhdujq      , id:4481   , score:461657936, num:258
name:rmg            , id:911109 , score:153943559, num:415
name:pmemwohbgqwwg  , id:789387 , score:257570203, num:481
name:wvukciloi      , id:734835 , score:416874932, num:605
name:benijj         , id:1867600, score:39352766, num:658
name:fisp           , id:1611284, score:194548462, num:734
name:xfjvbgocgnvgfr , id:995733 , score:181002072, num:834
name:jhxubuhgldh    , id:476109 , score:435832437, num:969

However, the sort was not performed. Vector's content was same before and after sort.

What did I miss? Is there a problem with Pointer or reference?