字符串与数字互相转换模板.cpp
string numStr = "123";
int x = stoi(numStr);
cout << x + 1 << '\n';
string piStr = "3.14";
double pi = stod(piStr);
cout << fixed << setprecision(2);
cout << pi * 2 << '\n';
int id = 42;
string idStr = to_string(id);
cout << "id = " << idStr << '\n';