你可以用c++帮我写一个简单的快件管理系统吗，要求进入系统后首先选择取件人模式或管理员模式，内置管理员的账号密码，取件人可以凭借手机号或者快递单号取快递，管理员可以进行快件的录入，删除，读取，修改，查询已取快件，查询未取快件，一个快件应包含的信息有：随机生成的快递单号，寄件人，寄件人手机号，寄件人住址，收件人，收件人手机号，收件人住址

好的，我可以帮您写一个简单的快件管理系统。以下是一个简单的C++代码示例，其中包含了管理员和取件人两种模式，以及快递的录入、删除、读取、修改、查询已取快件和查询未取快件等功能。

#include <iostream>
#include <string>
#include <vector>
#include <ctime>
#include <cstdlib>

using namespace std;

// 快递的结构体
struct Package {
    string package_id;      // 快递单号
    string sender_name;     // 寄件人
    string sender_phone;    // 寄件人手机号
    string sender_address;  // 寄件人住址
    string receiver_name;   // 收件人
    string receiver_phone;  // 收件人手机号
    string receiver_address;// 收件人住址
    bool taken;             // 是否已取件
};

// 管理员账号和密码
const string ADMIN_USERNAME = "admin";
const string ADMIN_PASSWORD = "123456";

// 快递列表
vector<Package> package_list;

// 生成随机的快递单号
string generate_package_id() {
    srand(time(NULL));  // 设置随机数种子
    string package_id = "KD" + to_string(rand() % 10000);
    return package_id;
}

// 快递录入
void add_package() {
    Package package;
    package.package_id = generate_package_id();
    cout << "请输入寄件人姓名：";
    cin >> package.sender_name;
    cout << "请输入寄件人手机号：";
    cin >> package.sender_phone;
    cout << "请输入寄件人住址：";
    cin >> package.sender_address;
    cout << "请输入收件人姓名：";
    cin >> package.receiver_name;
    cout << "请输入收件人手机号：";
    cin >> package.receiver_phone;
    cout << "请输入收件人住址：";
    cin >> package.receiver_address;
    package.taken = false;
    package_list.push_back(package);
    cout << "快递录入成功，快递单号为：" << package.package_id << endl;
}

// 快递删除
void delete_package() {
    string package_id;
    cout << "请输入要删除的快递单号：";
    cin >> package_id;
    bool found = false;
    for (int i = 0; i < package_list.size(); i++) {
        if (package_list[i].package_id == package_id) {
            package_list.erase(package_list.begin() + i);
            cout << "快递删除成功！" << endl;
            found = true;
            break;
        }
    }
    if (!found) {
        cout << "未找到快递单号为 " << package_id << " 的快递！" << endl;
    }
}

// 快递读取
void read_package() {
    string package_id;
    cout << "请输入要读取的快递单号：";
    cin >> package_id;
    bool found = false;
    for (Package package : package_list) {
        if (package.package_id == package_id) {
            cout << "快递单号：" << package.package_id << endl;
            cout << "寄件人姓名：" << package.sender_name << endl;
            cout << "寄件人手机号：" << package.sender_phone << endl;
            cout << "寄件人住址：" << package.sender_address << endl;
            cout << "收件人姓名：" << package.receiver_name << endl;
            cout << "收件人手机号：" << package.receiver_phone << endl;
            cout << "收件人住址：" << package.receiver_address << endl;
            cout << "是否已取件：" << (package.taken ? "是" : "否") << endl;
            found = true;
            break;
        }
    }
    if (!found) {
        cout << "未找到快递单号为 " << package_id << " 的快递！" << endl;
    }
}

// 快递修改
void modify_package() {
    string package_id;
    cout << "请输入要修改的快递单号：";
    cin >> package_id;
    bool found = false;
    for (Package &package : package_list) {
        if (package.package_id == package_id) {
            cout << "请输入新的寄件人姓名：";
            cin >> package.sender_name;
            cout << "请输入新的寄件人手机号：";
            cin >> package.sender_phone;
            cout << "请输入新的寄件人住址：";
            cin >> package.sender_address;
            cout << "请输入新的收件人姓名：";
            cin >> package.receiver_name;
            cout << "请输入新的收件人手机号：";
            cin >> package.receiver_phone;
            cout << "请输入新的收件人住址：";
            cin >> package.receiver_address;
            cout << "快递信息修改成功！" << endl;
            found = true;
            break;
        }
    }
    if (!found) {
        cout << "未找到快递单号为 " << package_id << " 的快递！" << endl;
    }
}

// 查询已取快件
void query_taken_packages() {
    int count = 0;
    for (Package package : package_list) {
        if (package.taken) {
            cout << "快递单号：" << package.package_id << endl;
            cout << "寄件人姓名：" << package.sender_name << endl;
            cout << "寄件人手机号：" << package.sender_phone << endl;
            cout << "寄件人住址：" << package.sender_address << endl;
            cout << "收件人姓名：" << package.receiver_name << endl;
            cout << "收件人手机号：" << package.receiver_phone << endl;
            cout << "收件人住址：" << package.receiver_address << endl;
            cout << "是否已取件：" << (package.taken ? "是" : "否") << endl;
            count++;
        }
    }
    if (count == 0) {
        cout << "没有已取快件！" << endl;
    }
}

// 查询未取快件
void query_untaken_packages() {
    int count = 0;
    for (Package package : package_list) {
        if (!package.taken) {
            cout << "快递单号：" << package.package_id << endl;
            cout << "寄件人姓名：" << package.sender_name << endl;
            cout << "寄件人手机号：" << package.sender_phone << endl;
            cout << "寄件人住址：" << package.sender_address << endl;
            cout << "收件人姓名：" << package.receiver_name << endl;
            cout << "收件人手机号：" << package.receiver_phone << endl;
            cout << "收件人住址：" << package.receiver_address << endl;
            cout << "是否已取件：" << (package.taken ? "是" : "否") << endl;
            count++;
        }
    }
    if (count == 0) {
        cout << "没有未取快件！" << endl;
    }
}

int main() {
    string username, password;
    cout << "欢迎使用快件管理系统！" << endl;
    cout << "请选择您的身份：" << endl;
    cout << "1. 取件人" << endl;
    cout << "2. 管理员" << endl;
    cout << "请选择：";
    int mode;
    cin >> mode;
    if (mode == 1) {
        bool found = false;
        string phone;
        cout << "请输入您的手机号：";
        cin >> phone;
        for (Package &package : package_list) {
            if (package.receiver_phone == phone && !package.taken) {
                cout << "您的快递已准备好，请前往取件！" << endl;
                package.taken = true;
                found = true;
                break;
            }
        }
        if (!found) {
            cout << "未找到您的快递，请检查手机号是否正确或快递是否已取件！" << endl;
        }
    } else if (mode == 2) {
        cout << "请输入管理员账号和密码：" << endl;
        cout << "账号：";
        cin >> username;
        cout << "密码：";
        cin >> password;
        if (username == ADMIN_USERNAME && password == ADMIN_PASSWORD) {
            cout << "管理员登录成功！" << endl;
            while (true) {
                cout << "请选择操作：" << endl;
                cout << "1. 录入快递" << endl;
                cout << "2. 删除快递" << endl;
                cout << "3. 读取快递" << endl;
                cout << "4. 修改快递" << endl;
                cout << "5. 查询已取快件" << endl;
                cout << "6. 查询未取快件" << endl;
                cout << "7. 退出" << endl;
                cout << "请选择：";
                int choice;
                cin >> choice;
                switch (choice) {
                    case 1:
                        add_package();
                        break;
                    case 2:
                        delete_package();
                        break;
                    case 3:
                        read_package();
                        break;
                    case 4:
                        modify_package();
                        break;
                    case 5:
                        query_taken_packages();
                        break;
                    case 6:
                        query_untaken_packages();
                        break;
                    case 7:
                        cout << "谢谢使用快件管理系统！" << endl;
                        return 0;
                    default:
                        cout << "输入有误，请重新输入！" << endl;
                }
            }
        } else {
            cout << "管理员账号或密码错误！" << endl;
        }
    } else {
        cout << "输入有误，请重新运行程序！" << endl;
    }
    return 0;
}

注意：以上代码只是一个简单的示例，可能存在一些不足之处，您可以根据自己的需求进行修改和完善。