C++ を使用して簡単な病院登録システムを作成するにはどうすればよいですか?

#include <iostream>
#include <vector>

struct Doctor {
    int id;
    std::string name;
    std::string specialty;
};

struct Patient {
    int id;
    std::string name;
    int age;
};

struct Appointment {
    int id;
    Doctor doctor;
    Patient patient;
    std::string date;
};

std::vector<Appointment> database;

void addDoctor() {
    Doctor doctor;
    
    // 从用户输入获取医生的信息
    std::cout << "请输入医生的编号：";
    std::cin >> doctor.id;
    std::cout << "请输入医生的姓名：";
    std::cin >> doctor.name;
    std::cout << "请输入医生的专业：";
    std::cin >> doctor.specialty;
    
    // 将医生添加到数据库中
    database.push_back(doctor);
}

void addPatient() {
    Patient patient;
    
    // 从用户输入获取患者的信息
    std::cout << "请输入患者的编号：";
    std::cin >> patient.id;
    std::cout << "请输入患者的姓名：";
    std::cin >> patient.name;
    std::cout << "请输入患者的年龄：";
    std::cin >> patient.age;
    
    // 将患者添加到数据库中
    database.push_back(patient);
}

void createAppointment() {
    Appointment appointment;
    
    // 从用户输入获取预约的信息
    std::cout << "请输入预约的编号：";
    std::cin >> appointment.id;
    
    // 从数据库中选择医生和患者
    std::cout << "医生列表：" << std::endl;
    for (const auto& doctor : database) {
        if (doctor.id >= 0) {
            std::cout << doctor.id << ": " << doctor.name << " - " << doctor.specialty << std::endl;
        }
    }
    std::cout << "请选择医生编号：";
    std::cin >> appointment.doctor.id;
    
    std::cout << "患者列表：" << std::endl;
    for (const auto& patient : database) {
        if (patient.id >= 0) {
            std::cout << patient.id << ": " << patient.name << " - " << patient.age << std::endl;
        }
    }
    std::cout << "请选择患者编号：";
    std::cin >> appointment.patient.id;
    
    std::cout << "请输入预约的日期：";
    std::cin >> appointment.date;
    
    // 将预约添加到数据库中
    database.push_back(appointment);
}

int main() {
    while (true) {
        std::cout << "欢迎使用医院挂号系统！" << std::endl;
        std::cout << "[1] 添加医生" << std::endl;
        std::cout << "[2] 添加患者" << std::endl;
        std::cout << "[3] 创建预约" << std::endl;
        std::cout << "[4] 退出系统" << std::endl;
        
        int choice;
        std::cout << "请选择功能：";
        std::cin >> choice;
        
        switch (choice) {
            case 1:
                addDoctor();
                break;
            case 2:
                addPatient();
                break;
            case 3:
                createAppointment();
                break;
            case 4:
                return 0;
        }
        
        std::cout << std::endl;
    }
    
    return 0;
}