运用C++知识编写程序。 题目: 实现一个简单的图书管理系统 程序内容要求： 1.创建类，根据题目要求，设计类所需的成员函数、数据成员。（要求类包含构造函数、析构函数、复制构造函数、友元或静态成员、

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

class Book {
private:
    std::string title;
    std::string author;
    int year;
public:
    Book(std::string t, std::string a, int y) : title(t), author(a), year(y) {}
    
    std::string getTitle() const {
        return title;
    }

    std::string getAuthor() const {
        return author;
    }

    int getYear() const {
        return year;
    }

    friend std::ostream& operator<<(std::ostream& os, const Book& book) {
        os << book.title << " by " << book.author << " (" << book.year << ")";
        return os;
    }
};

class Library {
private:
    std::vector<Book> books;
public:
    void addBook(const Book& book) {
        books.push_back(book);
    }

    void displayBooks() const {
        for (const Book& book : books) {
            std::cout << book << std::endl;
        }
    }
}