用c++写一个民航订票系统,要求使用文件储存数据，不使用链表、vector、数据库，有管理员类，实现查询航班、增加航班、删除航班、修改航班、显示航班等功能。

以下是一个简单的民航订票系统的代码示例：

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

using namespace std;

// 航班类
class Flight {
public:
    Flight() {}
    Flight(string num, string start, string end, string time) : num_(num), start_(start), end_(end), time_(time) {}

    // 获取航班号
    string GetNum() const {
        return num_;
    }

    // 获取起点
    string GetStart() const {
        return start_;
    }

    // 获取终点
    string GetEnd() const {
        return end_;
    }

    // 获取时间
    string GetTime() const {
        return time_;
    }

    // 设置航班信息
    void SetFlight(string num, string start, string end, string time) {
        num_ = num;
        start_ = start;
        end_ = end;
        time_ = time;
    }

private:
    string num_;    // 航班号
    string start_;  // 起点
    string end_;    // 终点
    string time_;   // 时间
};

// 管理员类
class Admin {
public:
    // 构造函数
    Admin() {
        LoadData();
    }

    // 析构函数
    ~Admin() {
        SaveData();
    }

    // 显示菜单
    void ShowMenu() {
        cout << "1. 查询航班" << endl;
        cout << "2. 增加航班" << endl;
        cout << "3. 删除航班" << endl;
        cout << "4. 修改航班" << endl;
        cout << "5. 显示航班" << endl;
        cout << "6. 退出系统" << endl;
    }

    // 查询航班
    void QueryFlight() {
        string num;
        cout << "请输入航班号：";
        cin >> num;

        if (flight_map_.count(num) == 0) {
            cout << "该航班不存在！" << endl;
        }
        else {
            Flight flight = flight_map_[num];
            cout << "航班号：" << flight.GetNum() << endl;
            cout << "起点：" << flight.GetStart() << endl;
            cout << "终点：" << flight.GetEnd() << endl;
            cout << "时间：" << flight.GetTime() << endl;
        }
    }

    // 增加航班
    void AddFlight() {
        string num, start, end, time;
        cout << "请输入航班号：";
        cin >> num;

        if (flight_map_.count(num) > 0) {
            cout << "该航班已存在！" << endl;
        }
        else {
            cout << "请输入起点：";
            cin >> start;
            cout << "请输入终点：";
            cin >> end;
            cout << "请输入时间：";
            cin >> time;

            Flight flight(num, start, end, time);
            flight_map_.insert(make_pair(num, flight));
            cout << "添加成功！" << endl;
        }
    }

    // 删除航班
    void DeleteFlight() {
        string num;
        cout << "请输入航班号：";
        cin >> num;

        if (flight_map_.count(num) == 0) {
            cout << "该航班不存在！" << endl;
        }
        else {
            flight_map_.erase(num);
            cout << "删除成功！" << endl;
        }
    }

    // 修改航班
    void ModifyFlight() {
        string num;
        cout << "请输入航班号：";
        cin >> num;

        if (flight_map_.count(num) == 0) {
            cout << "该航班不存在！" << endl;
        }
        else {
            string start, end, time;
            cout << "请输入起点（原：" << flight_map_[num].GetStart() << "）：";
            cin >> start;
            cout << "请输入终点（原：" << flight_map_[num].GetEnd() << "）：";
            cin >> end;
            cout << "请输入时间（原：" << flight_map_[num].GetTime() << "）：";
            cin >> time;

            Flight flight(num, start, end, time);
            flight_map_[num] = flight;
            cout << "修改成功！" << endl;
        }
    }

    // 显示航班
    void ShowFlight() {
        cout << "航班信息如下：" << endl;
        for (auto it = flight_map_.begin(); it != flight_map_.end(); ++it) {
            cout << "航班号：" << it->second.GetNum() << endl;
            cout << "起点：" << it->second.GetStart() << endl;
            cout << "终点：" << it->second.GetEnd() << endl;
            cout << "时间：" << it->second.GetTime() << endl;
            cout << endl;
        }
    }

    // 加载数据
    void LoadData() {
        ifstream fin("data.txt");
        if (fin.is_open()) {
            string num, start, end, time;
            while (fin >> num >> start >> end >> time) {
                Flight flight(num, start, end, time);
                flight_map_.insert(make_pair(num, flight));
            }
            fin.close();
        }
    }

    // 保存数据
    void SaveData() {
        ofstream fout("data.txt");
        if (fout.is_open()) {
            for (auto it = flight_map_.begin(); it != flight_map_.end(); ++it) {
                fout << it->second.GetNum() << " " << it->second.GetStart() << " " << it->second.GetEnd() << " " << it->second.GetTime() << endl;
            }
            fout.close();
        }
    }

private:
    map<string, Flight> flight_map_;    // 航班信息
};

int main() {
    Admin admin;
    int choice;

    do {
        admin.ShowMenu();
        cout << "请输入选择：";
        cin >> choice;

        switch (choice) {
        case 1:
            admin.QueryFlight();
            break;
        case 2:
            admin.AddFlight();
            break;
        case 3:
            admin.DeleteFlight();
            break;
        case 4:
            admin.ModifyFlight();
            break;
        case 5:
            admin.ShowFlight();
            break;
        case 6:
            break;
        default:
            cout << "输入有误，请重新输入！" << endl;
            break;
        }
    } while (choice != 6);

    return 0;
}

在该示例代码中，使用了 `fstream` 头文件来读写数据文件，使用了 `map` 容器来存储航班信息，实现了管理员类的基本功能。注意，该示例只是一个简单的实现，对于复杂的民航订票系统还需要继续完善。