一道華爲筆試題

#include <iostream>

class human
{
public:
static int human_num;

human(){
human_num++;
std::cout<<"default human num is: "<<human_num<<std::endl;
};
human(const human& c){
std::cout<<"copy human num is: "<<human_num<<std::endl;
};

human operator=(const human& c){
std::cout<<"= human num is: "<<human_num<<std::endl;
int a = 2;
return c;
}

~human(){
human_num--;
std::cout<<"destruct human num is: "<<human_num<<std::endl;
}

void print()
{
std::cout<<"human num is: "<<human_num<<std::endl;
}

protected:
private:
};
int human::human_num = 0;
human& f1(human& x)
{
x.print();
return x;
}
int main(int argc, char* argv[])
{
human h1;
h1.print();
human h2 = f1(h1);
h2.print();
return 0;
}

//注意兩點:1.函數臨時返回對象就是傳入的實參旳副本，直到拷貝給其餘對象，再銷燬這個臨時對象。若是不拷貝則會當即銷燬。2.在聲明一個對象時若是同時賦值，則調用拷貝構造，省掉一個默認構造。這點很重要。