格式化输出模板.cpp
double pi = 3.1415926535;
int id = 7;
cout << fixed << setprecision(2);
cout << pi << '\n';
cout << setw(5) << id << '\n';
cout << setfill('0') << setw(5) << id << '\n';
double pi = 3.1415926535;
int id = 7;
cout << fixed << setprecision(2);
cout << pi << '\n';
cout << setw(5) << id << '\n';
cout << setfill('0') << setw(5) << id << '\n';