C++怎么在Clion里不能定义在使用之前啊

Question

#include
using namespace std;
class Time
{
public:
int hour;
int minute;
int sec;
};

int main()
{
void set_time(Time&);
void show_time(Time&);
Time t1;
set_time(t1);
show_time(t1);
return 0;
}
void set_time(Time& time1)
{
cin>>time1.hour>>time1.minute>>time1.sec;
}
void show_time(Time& time2)
{
cout<<time2.hour<<":"<<time2.minute<<":"<<time2.sec;
}

Answer 1

void set_time(Time&);
void show_time(Time&);
写在main()之前 不能写在里面