User* currentUser = nullptr; while (true) { cout << "1. Login" << endl; cout << "2. Register" << endl; cout

这段代码是一个简单的用户登录/注册系统，其中currentUser指针用于记录当前登录的用户。当用户选择登录时，程序会提示输入用户名和密码，并在用户列表中查找是否存在该用户，如果存在则将currentUser指向该用户；当用户选择注册时，程序会提示输入新用户的信息，并将该用户添加到用户列表中。 完整代码如下： ```c++ #include #include #include #include using namespace std; class User { public: string username; string password; }; vector users; User* currentUser = nullptr; void loadUsers() { ifstream fin("users.txt"); if (!fin) { cout << "Failed to open file: users.txt" << endl; return; } while (!fin.eof()) { User user; fin >> user.username >> user.password; if (user.username != "") { users.push_back(user); } } fin.close(); } void saveUsers() { ofstream fout("users.txt"); for (int i = 0; i < users.size(); i++) { fout << users[i].username << " " << users[i].password << endl; } fout.close(); } bool login() { string username, password; cout << "Username: "; cin >> username; cout << "Password: "; cin >> password; for (int i = 0; i < users.size(); i++) { if (users[i].username == username && users[i].password == password) { currentUser = &users[i]; return true; } } cout << "Invalid username or password." << endl; return false; } void registerUser() { string username, password; cout << "Username: "; cin >> username; for (int i = 0; i < users.size(); i++) { if (users[i].username == username) { cout << "Username already exists." << endl; return; } } cout << "Password: "; cin >> password; User user; user.username = username; user.password = password; users.push_back(user); saveUsers(); cout << "Registration successful." << endl; } int main() { load