c++某公司需要存储雇员的编号、姓名、性别、所在部门，级别，并进行工资的计算。其中的雇员分为经理、技术人员。月薪计算方法如下:经理拿固定目薪;技术人员按小时领取月薪。功能需求: (1)设计一程序能够对公司人员进行管理，应用到继承、抽象类、虚函数、虚基类、多态和文件的输入/输出等内容。 (2)添加功能:根据用户选择的人员类别，添加经理或者技术人员。要求员工的编号要唯一，如果添加了重复编号的记录时，则提示数据添加重复，并取消添加。 (3)查询功能:可根据编号、姓名等信息对已添加的记录进行查询，如果未找到，给出相应的提示信息，如果找到，则显示相应的记录信息;可显示当前系统中所有记录，每条记录占据一行。

这是一个比较典型的面向对象设计问题，需要考虑继承、类的关系以及多态的应用。以下是一个简单的设计方案：

1. 建立一个基类Employee，包含编号、姓名、性别、所在部门和级别等基本信息，以及计算月薪的纯虚函数calculateMonthlySalary()。
2. 派生出Manager类和Technician类，分别代表经理和技术人员。Manager类只需要重写calculateMonthlySalary()函数，计算固定目薪即可；Technician类需要增加一个小时工资的成员变量并重写calculateMonthlySalary()函数。
3. 建立一个EmployeeList类，用于管理所有员工的信息，包含一个vector<Employee*>类型的成员变量employees，用于存储所有员工的指针。
4. 在EmployeeList类中添加添加员工和查询员工的功能，可以通过员工类别、编号、姓名等信息进行查询。添加员工时需要检查是否有重复编号的记录。
5. 使用文件的输入/输出，将员工信息保存到文件中，以便下次程序运行时可以读取。

以下是一个简单的代码实现，仅供参考：

#include <iostream>
#include <vector>
#include <fstream>
using namespace std;

class Employee {
public:
    Employee(int id, string name, char gender, string department, string level)
        : m_id(id), m_name(name), m_gender(gender), m_department(department), m_level(level) {}
    virtual ~Employee() {}
    virtual double calculateMonthlySalary() = 0;
    int getId() const { return m_id; }
    string getName() const { return m_name; }
    char getGender() const { return m_gender; }
    string getDepartment() const { return m_department; }
    string getLevel() const { return m_level; }
protected:
    int m_id;
    string m_name;
    char m_gender;
    string m_department;
    string m_level;
};

class Manager : public Employee {
public:
    Manager(int id, string name, char gender, string department, string level, double salary)
        : Employee(id, name, gender, department, level), m_salary(salary) {}
    double calculateMonthlySalary() { return m_salary; }
private:
    double m_salary;
};

class Technician : public Employee {
public:
    Technician(int id, string name, char gender, string department, string level, double hourlyWage)
        : Employee(id, name, gender, department, level), m_hourlyWage(hourlyWage) {}
    double calculateMonthlySalary() { return m_hourlyWage * 160; }
private:
    double m_hourlyWage;
};

class EmployeeList {
public:
    EmployeeList() {}
    ~EmployeeList() {
        for (auto it = employees.begin(); it != employees.end(); ++it) {
            delete *it;
        }
    }
    void addEmployee(Employee* employee) {
        for (auto it = employees.begin(); it != employees.end(); ++it) {
            if ((*it)->getId() == employee->getId()) {
                cout << "Error: Duplicate employee ID.\n";
                return;
            }
        }
        employees.push_back(employee);
    }
    Employee* findEmployeeById(int id) {
        for (auto it = employees.begin(); it != employees.end(); ++it) {
            if ((*it)->getId() == id) {
                return *it;
            }
        }
        return nullptr;
    }
    void printAllEmployees() {
        for (auto it = employees.begin(); it != employees.end(); ++it) {
            cout << (*it)->getId() << "\t" << (*it)->getName() << "\t"
                 << (*it)->getGender() << "\t" << (*it)->getDepartment() << "\t"
                 << (*it)->getLevel() << "\t" << (*it)->calculateMonthlySalary() << endl;
        }
    }
    void saveToFile(string filename) {
        ofstream ofs(filename);
        if (!ofs.is_open()) {
            cout << "Error: Cannot open file " << filename << " for writing.\n";
            return;
        }
        for (auto it = employees.begin(); it != employees.end(); ++it) {
            ofs << (*it)->getId() << "\t" << (*it)->getName() << "\t"
                << (*it)->getGender() << "\t" << (*it)->getDepartment() << "\t"
                << (*it)->getLevel() << "\t" << (*it)->calculateMonthlySalary() << endl;
        }
        ofs.close();
    }
    void loadFromFile(string filename) {
        ifstream ifs(filename);
        if (!ifs.is_open()) {
            cout << "Error: Cannot open file " << filename << " for reading.\n";
            return;
        }
        int id;
        string name, department, level;
        char gender;
        double salaryOrHourlyWage;
        while (ifs >> id >> name >> gender >> department >> level >> salaryOrHourlyWage) {
            if (level == "Manager") {
                employees.push_back(new Manager(id, name, gender, department, level, salaryOrHourlyWage));
            } else if (level == "Technician") {
                employees.push_back(new Technician(id, name, gender, department, level, salaryOrHourlyWage));
            }
        }
        ifs.close();
    }
private:
    vector<Employee*> employees;
};

int main() {
    EmployeeList list;
    list.loadFromFile("employees.txt");

    while (true) {
        cout << "1. Add employee\n";
        cout << "2. Find employee\n";
        cout << "3. Print all employees\n";
        cout << "4. Save to file\n";
        cout << "5. Exit\n";
        int choice;
        cout << "Enter your choice: ";
        cin >> choice;
        if (choice == 1) {
            cout << "1. Manager\n";
            cout << "2. Technician\n";
            int type;
            cout << "Enter employee type: ";
            cin >> type;
            if (type == 1) {
                int id;
                string name, department, level;
                char gender;
                double salary;
                cout << "Enter employee ID: ";
                cin >> id;
                cout << "Enter employee name: ";
                cin >> name;
                cout << "Enter employee gender: ";
                cin >> gender;
                cout << "Enter employee department: ";
                cin >> department;
                cout << "Enter employee level: ";
                cin >> level;
                cout << "Enter employee salary: ";
                cin >> salary;
                list.addEmployee(new Manager(id, name, gender, department, level, salary));
            } else if (type == 2) {
                int id;
                string name, department, level;
                char gender;
                double hourlyWage;
                cout << "Enter employee ID: ";
                cin >> id;
                cout << "Enter employee name: ";
                cin >> name;
                cout << "Enter employee gender: ";
                cin >> gender;
                cout << "Enter employee department: ";
                cin >> department;
                cout << "Enter employee level: ";
                cin >> level;
                cout << "Enter employee hourly wage: ";
                cin >> hourlyWage;
                list.addEmployee(new Technician(id, name, gender, department, level, hourlyWage));
            }
        } else if (choice == 2) {
            int id;
            cout << "Enter employee ID to find: ";
            cin >> id;
            Employee* employee = list.findEmployeeById(id);
            if (employee == nullptr) {
                cout << "Employee not found.\n";
            } else {
                cout << employee->getId() << "\t" << employee->getName() << "\t"
                     << employee->getGender() << "\t" << employee->getDepartment() << "\t"
                     << employee->getLevel() << "\t" << employee->calculateMonthlySalary() << endl;
            }
        } else if (choice == 3) {
            list.printAllEmployees();
        } else if (choice == 4) {
            list.saveToFile("employees.txt");
        } else if (choice == 5) {
            break;
        }
    }

    return 0;
}

在以上代码中，我们使用了vector来存储所有员工的指针，并且在EmployeeList类的析构函数中遍历所有指针并释放内存。在添加员工和查询员工时，我们遍历vector来查找对应的员工指针。在保存和读取文件时，我们使用了fstream库提供的文件输入/输出功能，将员工信息保存到文件中或从文件中读取。