图书管理 运用C++语言描述书籍类、图书类型类、图书类。设计基类和派生类，并运用多态性和虚函数的知识。要求设计具有继承与派生以及多态性的类。 要实现的主要功能如下： 1）建立书籍类、图书类型类、图书类 2）书籍、图书类型、图书信息的初始化 3）书籍、图书类型、图书信息的添加、修改、删除、查找 4）图书信息的输出 5）对图书信息按编号、书名排序 6）将图书信息保存为文件

好的，下面是一个简单的C++代码示例，实现了书籍类(Book)、图书类型类(BookType)、图书类(Library)以及对图书信息的添加、修改、删除、查找、排序和输出等功能。同时，使用了多态性和虚函数的知识。

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

using namespace std;

// 基类：书籍类
class Book {
protected:
    string title;
    string author;
    string publisher;
    int year;
    int pages;
public:
    Book(string t = "", string a = "", string p = "", int y = 0, int pg = 0)
     : title(t), author(a), publisher(p), year(y), pages(pg) {}
    virtual ~Book() {}
    virtual void display() const = 0;  // 纯虚函数
    virtual void input() {
        cout << "Title: ";
        getline(cin, title);
        cout << "Author: ";
        getline(cin, author);
        cout << "Publisher: ";
        getline(cin, publisher);
        cout << "Publication Year: ";
        cin >> year;
        cout << "Number of Pages: ";
        cin >> pages;
        cin.ignore();  // 忽略换行符
    }
    string getTitle() const {
        return title;
    }
    string getAuthor() const {
        return author;
    }
    string getPublisher() const {
        return publisher;
    }
    int getYear() const {
        return year;
    }
    int getPages() const {
        return pages;
    }
};

// 派生类：图书类型类
class BookType : public Book {
private:
    string type;
public:
    BookType(string t = "", string a = "", string p = "", int y = 0, int pg = 0, string tp = "")
     : Book(t, a, p, y, pg), type(tp) {}
    void display() const {
        cout << "Title: " << title << endl;
        cout << "Author: " << author << endl;
        cout << "Publisher: " << publisher << endl;
        cout << "Publication Year: " << year << endl;
        cout << "Number of Pages: " << pages << endl;
        cout << "Type: " << type << endl << endl;
    }
    void input() {
        Book::input();
        cout << "Type: ";
        getline(cin, type);
    }
    string getType() const {
        return type;
    }
};

// 派生类：图书类
class Library : public Book {
private:
    int id;  // 图书编号
    static int count;  // 统计图书数目
public:
    Library(string t = "", string a = "", string p = "", int y = 0, int pg = 0)
     : Book(t, a, p, y, pg), id(++count) {}
    void display() const {
        cout << "ID: " << id << endl;
        cout << "Title: " << title << endl;
        cout << "Author: " << author << endl;
        cout << "Publisher: " << publisher << endl;
        cout << "Publication Year: " << year << endl;
        cout << "Number of Pages: " << pages << endl << endl;
    }
    void input() {
        Book::input();
    }
    int getID() const {
        return id;
    }
    // 按编号排序
    static bool cmpID(const Library& l1, const Library& l2) {
        return l1.id < l2.id;
    }
    // 按书名排序
    static bool cmpTitle(const Library& l1, const Library& l2) {
        return l1.title < l2.title;
    }
};

int Library::count = 0;  // 初始化静态成员变量

// 图书管理类
class BookManager {
private:
    vector<Book*> books;  // 所有图书的指针数组
public:
    ~BookManager() {
        for (int i = 0; i < books.size(); i++) {
            delete books[i];
        }
    }
    // 添加书籍
    void addBook(Book* book) {
        books.push_back(book);
    }
    // 修改书籍
    void modifyBook(int id) {
        for (int i = 0; i < books.size(); i++) {
            Library* lib = dynamic_cast<Library*>(books[i]);  // 动态类型转换
            if (lib != nullptr && lib->getID() == id) {
                lib->input();
                cout << "Book modified successfully!" << endl << endl;
                return;
            }
        }
        cout << "Book not found!" << endl << endl;
    }
    // 删除书籍
    void removeBook(int id) {
        for (int i = 0; i < books.size(); i++) {
            Library* lib = dynamic_cast<Library*>(books[i]);
            if (lib != nullptr && lib->getID() == id) {
                books.erase(books.begin() + i);
                cout << "Book removed successfully!" << endl << endl;
                return;
            }
        }
        cout << "Book not found!" << endl << endl;
    }
    // 查找书籍
    void searchBook(string keyword) {
        for (int i = 0; i < books.size(); i++) {
            Library* lib = dynamic_cast<Library*>(books[i]);
            if (lib != nullptr && (lib->getTitle().find(keyword) != string::npos || 
                                   lib->getAuthor().find(keyword) != string::npos)) {
                books[i]->display();
            }
        }
    }
    // 按编号排序
    void sortByID() {
        sort(books.begin(), books.end(), Library::cmpID);
    }
    // 按书名排序
    void sortByTitle() {
        sort(books.begin(), books.end(), Library::cmpTitle);
    }
    // 输出所有图书信息
    void displayAll() {
        for (int i = 0; i < books.size(); i++) {
            books[i]->display();
        }
    }
    // 保存图书信息到文件
    void saveToFile(string filename) {
        ofstream fout(filename);
        if (!fout) {
            cout << "Failed to open file: " << filename << endl;
            return;
        }
        for (int i = 0; i < books.size(); i++) {
            fout << books[i]->getTitle() << '\t' << books[i]->getAuthor() << '\t' 
                 << books[i]->getPublisher() << '\t' << books[i]->getYear() << '\t' 
                 << books[i]->getPages() << '\t';
            Library* lib = dynamic_cast<Library*>(books[i]);
            if (lib != nullptr) {
                fout << lib->getID();
            }
            fout << endl;
        }
        fout.close();
        cout << "Books saved to file: " << filename << endl << endl;
    }
};

int main() {
    BookManager manager;
    while (true) {
        cout << "1. Add Book" << endl;
        cout << "2. Modify Book" << endl;
        cout << "3. Remove Book" << endl;
        cout << "4. Search Book" << endl;
        cout << "5. Sort by ID" << endl;
        cout << "6. Sort by Title" << endl;
        cout << "7. Display All Books" << endl;
        cout << "8. Save to File" << endl;
        cout << "0. Exit" << endl;
        int choice;
        cin >> choice;
        cin.ignore();  // 忽略换行符
        cout << endl;
        switch (choice) {
            case 1: {
                cout << "1. Book Type" << endl;
                cout << "2. Library" << endl;
                int type;
                cin >> type;
                cin.ignore();
                if (type == 1) {
                    BookType* book = new BookType();
                    book->input();
                    manager.addBook(book);
                } else if (type == 2) {
                    Library* book = new Library();
                    book->input();
                    manager.addBook(book);
                } else {
                    cout << "Invalid choice!" << endl << endl;
                }
                break;
            }
            case 2: {
                int id;
                cout << "Enter Book ID: ";
                cin >> id;
                manager.modifyBook(id);
                break;
            }
            case 3: {
                int id;
                cout << "Enter Book ID: ";
                cin >> id;
                manager.removeBook(id);
                break;
            }
            case 4: {
                string keyword;
                cout << "Enter Keyword: ";
                getline(cin, keyword);
                manager.searchBook(keyword);
                break;
            }
            case 5: {
                manager.sortByID();
                cout << "Books sorted by ID." << endl << endl;
                break;
            }
            case 6: {
                manager.sortByTitle();
                cout << "Books sorted by Title." << endl << endl;
                break;
            }
            case 7: {
                manager.displayAll();
                break;
            }
            case 8: {
                string filename;
                cout << "Enter Filename: ";
                getline(cin, filename);
                manager.saveToFile(filename);
                break;
            }
            case 0: {
                return 0;
            }
            default: {
                cout << "Invalid choice!" << endl << endl;
                break;
            }
        }
    }
}

该程序通过使用基类和派生类，实现了对书籍信息的建立，图书类型类和图书类继承自书籍类，同时使用了多态性和虚函数的知识，其中图书类(Library)还添加了一个静态成员变量count，统计图书数目。程序实现了对图书信息的初始化、添加、修改、删除、查找、排序和输出等功能，并可以将图书信息保存到文件中。