按 c++ asc 和 desc 顺序对向量进行排序

Question

我有 Player 类，我必须创建静态方法 void Player::sortPlayers( vector<Player> &players, bool (*c)(const Player&, const Player&)) 并且该方法应该只包含一行，您可以在其中调用函数 sort ，您可以使用该函数将玩家按年龄升序或降序排列，而不是在 main创建两个函数bool ascending(const Player &p1, const Player&p2) 和 bool descending(const Player &p1, const Player &p)。 我在课堂上做过：

void Player::sortPlayers(vector<Player> &players, bool (*c)(const Player&, const Player&)) {
sort(players.begin(),players.end());
}

如何从 main 开始？我试过了，但它不起作用（对于 asc）：

bool ascending(const Player &p1, const Player &p2) {
    Player::sortPlayers(p1,p2);
}

错误信息： Non-const lvalue reference to type 'vector<Player>' cannot bind to a value of unrelated type 'const Player'

Answer 1

std::sort 需要三个参数，第三个是比较器。您可以定义比较器以使 std::sort 适合您的需求，如下所示

void Player::sortPlayers(vector<Player> &players, bool (*c)(const Player&, const Player&)) {//define sortPlayers function
std::sort(players.begin(),players.end(), c);
}


bool ascending(const Player &p1, const Player &p2) {//define ascending function here
    return p1.age < p2.age;
}

bool descending(const Player &p1, const Player &p2) {//define descending function here
    return p1.age > p2.age;
}

int main()
{
    std::vector<Player> players = ....;//initialize the vector of players here
    Players::sortPlayers(players, ascending);//sort them in ascending order
    Players::sortPlayers(players, descending);//sort them in descending order

}