给代码加入用户密码功能，使用户注册时需要设置密码，登陆时需要输入密码，写出完整代码并且可以运行

为了实现用户密码的功能，我们需要在 `User` 类中增加一个私有成员变量来存储密码，并且提供相应的 setter 和 getter 方法来处理密码的设置和获取。此外，在 `BikeRentalSystem` 类中的用户注册和登录方法也需要进行调整以支持密码验证。

以下是修改后的代码：

#include <iostream>
#include <fstream>
#include< string >
#include <vector>

// 定义用户类
class User {
private:
    std::string username;
    std::string gender;
    int age;
    std::string idNumber;
    std::string phoneNumber;
    std::string occupation;
    std::string address;
    double accountBalance;
    std::string password;

public:
    // 构造函数
    User(std::string username, std::string gender, int age, std::string idNumber,
         std::string phoneNumber, std::string occupation, std::string address,
         double accountBalance, std::string password)
        : username(username), gender(gender), age(age), idNumber(idNumber),
          phoneNumber(phoneNumber), occupation(occupation), address(address),
          accountBalance(accountBalance), password(password) {}

    // 获取用户名
    std::string getUsername() const { return username; }

    // 获取性别
    std::string getGender() const { return gender; }

    // 获取年龄
    int getAge() const { return age; }

    // 获取身份证号码
    std::string getIdNumber() const { return idNumber; }

    // 获取手机号码
    std::string getPhoneNumber() const { return phoneNumber; }

    // 获取职业
    std::string getOccupation() const { return occupation; }

    // 获取家庭住址
    std::string getAddress() const { return address; }

    // 获取账户余额
    double getAccountBalance() const { return accountBalance; }

    // 获取密码
    std::string getPassword() const { return password; }

    // 充值
    void recharge(double amount) { accountBalance += amount; }

    // 扣除金额
    void deduct(double amount) { accountBalance -= amount; }
};

// 定义自行车类
class Bike {
private:
    std::string bikeName;
    std::string parkingLocation;

public:
    // 构造函数
    Bike(std::string bikeName, std::string parkingLocation)
        : bikeName(bikeName), parkingLocation(parkingLocation) {}

    // 获取自行车名称
    std::string getBikeName() const { return bikeName; }

    // 获取停车位置
    std::string getParkingLocation() const { return parkingLocation; }

    // 设置停车位置
    void setParkingLocation(std::string location) { parkingLocation = location; }
};

// 定义自行车租赁管理系统类
class BikeRentalSystem {
private:
    std::vector<User> users;
    std::vector<Bike> bikes;
    std::string userFile;
    std::string bikeFile;

public:
    // 构造函数
    BikeRentalSystem(std::string userFile, std::string bikeFile)
        : userFile(userFile), bikeFile(bikeFile) {}

    // 添加用户
    void addUser(User user) { users.push_back(user); }

    // 删除用户
    void deleteUser(std::string username) {
        for (auto it = users.begin(); it != users.end(); ++it) {
            if (it->getUsername() == username) {
                users.erase(it);
                break;
            }
        }
    }

    // 修改用户信息
    void modifyUser(User user) {
        for (auto& u : users) {
            if (u.getUsername() == user.getUsername()) {
                u = user;
                break;
            }
        }
    }

    // 查找用户
    User* findUser(std::string username) {
        for (auto& u : users) {
            if (u.getUsername() == username) {
                return &u;
            }
        }
        return nullptr;
    }

    // 添加自行车
    void addBike(Bike bike) { bikes.push_back(bike); }

    // 删除自行车
    void deleteBike(std::string bikeName) {
        for (auto it = bikes.begin(); it != bikes.end(); ++it) {
            if (it->getBikeName() == bikeName) {
                bikes.erase(it);
                break;
            }
        }
    }

    // 修改自行车信息
    void modifyBike(Bike bike) {
        for (auto& b : bikes) {
            if (b.getBikeName() == bike.getBikeName()) {
                b = bike;
                break;
            }
        }
    }

    // 查找自行车
    Bike* findBike(std::string bikeName) {
        for (auto& b : bikes) {
            if (b.getBikeName() == bikeName) {
                return &b;
            }
        }
        return nullptr;
    }

    // 自行车借出
    void rentBike(std::string username, std::string bikeName) {
        User* user = findUser(username);
        Bike* bike = findBike(bikeName);
        if (user && bike && bike->getParkingLocation() != "") {
            user->deduct(10.0); // 扣除租金
            bike->setParkingLocation(""); // 更新自行车停车位置为空
            std::cout << "租车成功！" << std::endl;
        } else {
            std::cout << "租车失败！" << std::endl;
        }
    }

    // 自行车归还
    void returnBike(std::string username, std::string bikeName) {
        User* user = findUser(username);
        Bike* bike = findBike(bikeName);
        if (user && bike && bike->getParkingLocation() == "") {
            user->recharge(5.0); // 退还押金
            bike->setParkingLocation("停车点"); // 更新自行车停车位置
            std::cout << "还车成功！" << std::endl;
        } else {
            std::cout << "还车失败！" << std::endl;
        }
    }

    // 显示用户信息
    void displayUserInfo(std::string username) {
        User* user = findUser(username);
        if (user) {
            std::cout << "用户名：" << user->getUsername() << std::endl;
            std::cout << "性别：" << user->getGender() << std::endl;
            std::cout << "年龄：" << user->getAge() << std::endl;
            std::cout << "身份证号码：" << user->getIdNumber() << std::endl;
            std::cout << "手机号码：" << user->getPhoneNumber() << std::endl;
            std::cout << "职业：" << user->getOccupation() << std::endl;
            std::cout << "家庭住址：" << user->getAddress() << std::endl;
            std::cout << "账户余额：" << user->getAccountBalance() << std::endl;
        } else {
            std::cout << "用户不存在！" << std::endl;
        }
    }

    // 显示自行车信息
    void displayBikeInfo(std::string bikeName) {
        Bike* bike = findBike(bikeName);
        if (bike) {
            std::cout << "自行车名称：" << bike->getBikeName() << std::endl;
            std::cout << "停车位置：" << bike->getParkingLocation() << std::endl;
        } else {
            std::cout << "自行车不存在！" << std::endl;
        }
    }

    // 添加 getBikes 函数
    std::vector<Bike>& getBikes() { return bikes; }
};

int main() {
    BikeRentalSystem system("users.txt", "bikes.txt");
    int choice;
    std::string username, password, bikeName;
    do {
        std::cout << "自行车租赁管理系统" << std::endl;
        std::cout << "1. 用户注册" << std::endl;
        std::cout << "2. 用户登录" << std::endl;
        std::cout << "3. 管理员登录" << std::endl;
        std::cout << "4. 退出" << std::endl;
        std::cout << "请选择操作：";
        std::cin >> choice;
        switch (choice) {
            case 1: {
                std::string username, gender, idNumber, phoneNumber, occupation, address, password;
                int age;
                double accountBalance;
                std::cout << "请输入用户名：";
                std::cin >> username;
                std::cout << "请输入密码：";
                std::cin >> password;
                std::cout << "请输入性别：";
                std::cin >> gender;
                std::cout << "请输入年龄：";
                std::cin >> age;
                std::cout << "请输入身份证号码：";
                std::cin >> idNumber;
                std::cout << "请输入手机号码：";
                std::cin >> phoneNumber;
                std::cout << "请输入职业：";
                std::cin >> occupation;
                std::cout << "请输入家庭住址：";
                std::cin >> address;
                std::cout << "请输入初始账户余额：";
                std::cin >> accountBalance;
                User user(username, gender, age, idNumber, phoneNumber, occupation, address, accountBalance, password);
                system.addUser(user);
                std::cout << "用户注册成功！" << std::endl;
                break;
            }
            case 2: {
                std::cout << "请输入用户名：";
                std::cin >> username;
                std::cout << "请输入密码：";
                std::cin >> password;
                User* user = system.findUser(username);
                if (user && user->getPassword() == password) {
                    std::cout << "用户登录成功！" << std::endl;
                    int subChoice;
                    do {
                        std::cout << "1. 个人信息维护" << std::endl;
                        std::cout << "2. 车辆借出" << std::endl;
                        std::cout << "3. 车辆归还" << std::endl;
                        std::cout << "4. 充值" << std::endl;
                        std::cout << "5. 查看个人信息" << std::endl;
                        std::cout << "6. 查看车辆信息" << std::endl;
                        std::cout << "7. 退出" << std::endl;
                        std::cout << "请选择操作：";
                        std::cin >> subChoice;
                        switch (subChoice) {
                            case 1: {
                                std::string gender, idNumber, phoneNumber, occupation, address, password;
                                int age;
                                std::cout << "请输入性别：";
                                std::cin >> gender;
                                std::cout << "请输入年龄：";
                                std::cin >> age;
                                std::cout << "请输入身份证号码：";
                                std::cin >> idNumber;
                                std::cout << "请输入手机号码：";
                                std::cin >> phoneNumber;
                                std::cout << "请输入职业：";
                                std::cin >> occupation;
                                std::cout << "请输入家庭住址：";
                                std::cin >> address;
                                std::cout << "请输入新密码：";
                                std::cin >> password;
                                User updatedUser(username, gender, age, idNumber, phoneNumber, occupation, address, user->getAccountBalance(), password);
                                system.modifyUser(updatedUser);
                                std::cout << "个人信息维护成功！" << std::endl;
                                break;
                            }
                            case 2: {
                                std::cout << "请输入要借出的自行车名称：";
                                std::cin >> bikeName;
                                system.rentBike(username, bikeName);
                                break;
                            }
                            case 3: {
                                std::cout << "请输入要归还的自行车名称：";
                                std::cin >> bikeName;
                                system.returnBike(username, bikeName);
                                break;
                            }
                            case 4: {
                                double amount;
                                std::cout << "请输入充值金额：";
                                std::cin >> amount;
                                user->recharge(amount);
                                std::cout << "充值成功！" << std::endl;
                                break;
                            }
                            case 5: {
                                system.displayUserInfo(username);
                                break;
                            }
                            case 6: {
                                system.displayBikeInfo(bikeName);
                                break;
                            }
                            case 7: {
                                std::cout << "退出" << std::endl;
                                break;
                            }
                            default: {
                                std::cout << "无效的选择，请重新输入！" << std::endl;
                                break;
                            }
                        }
                    } while (subChoice != 7);
                } else {
                    std::cout << "用户不存在或密码错误！" << std::endl;
                }
                break;
            }
            case 3: {
                std::string adminUsername, adminPassword;
                std::cout << "请输入管理员用户名：";
                std::cin >> adminUsername;
                std::cout << "请输入管理员密码：";
                std::cin >> adminPassword;
                if (adminUsername == "admin" && adminPassword == "admin") {
                    std::cout << "管理员登录成功！" << std::endl;
                    int subChoice;
                    do {
                        std::cout << "1. 用户管理" << std::endl;
                        std::cout << "2. 自行车管理" << std::endl;
                        std::cout << "3. 营收管理" << std::endl;
                        std::cout << "4. 退出" << std::endl;
                        std::cout << "请选择操作：";
                        std::cin >> subChoice;
                        switch (subChoice) {
                            case 1: {
                                int userChoice;
                                std::cout << "1. 添加用户" << std::endl;
                                std::cout << "2. 删除用户" << std::endl;
                                std::cout << "3. 修改用户信息" << std::endl;
                                std::cout << "4. 查找用户" << std::endl;
                                std::cout << "5. 退出" << std::endl;
                                std::cout << "请选择操作：";
                                std::cin >> userChoice;
                                switch (userChoice) {
                                    case 1: {
                                        std::string username, gender, idNumber, phoneNumber, occupation, address, password;
                                        int age;
                                        double accountBalance;
                                        std::cout << "请输入用户名：";
                                        std::cin >> username