Question

我使用for循环和if-else语句尝试按字母顺序对书籍的标题进行排序。但是，我在returnlistofBooks方法下面临一些错误。有什么方法可以解决这个问题吗？

voidBookshelf::voidBookshelf(vector <Book*> listofBooks){
this->listofBooks = listofBooks;
}

void voidBookshelf::addBook()
 {
int ID;
string Title;
string Author;
for (int i = 1; i <= 5; i++)
    {
        cout << "Book#"<< i << ":" << endl;
        cout << "Enter an ID:";
        cin >> ID;
        cout << "Enter a title:";
        cin >> Title;
        cout << "Enter an author:";
        cin >> Author;
        Book *mybook = new Book(ID, Title, Author); //book object
        listofBooks.push_back(mybook);
       }

}

void returnListofBooks(int count, string name)
{
Book temp;
for (int i = 0; i < count; i++) 
{
    for (int j = 0; j < count - i; j++) 
    {
        if (books[j].author > books[j + 1].author) 
        {
            //swapping the instances themselves, but still comparing by the     member.
            temp = books[j];
            books[j] = books[j + 1];
            books[j + 1] = temp;
        }
    }
  }
}




int main(){

voidBookshelf * myBookshelf = new voidBookshelf;

myBookshelf->addBook();
myBookshelf->returnListofBooks();

return 0;

}

Answer 1

你可以在这里查看排序功能！它非常简单！去： http://www.cplusplus.com/articles/NhA0RXSz/

Answer 2

允许排序的简单方法是在类中重载operator<：

class Book
{
  public:
    bool operator< (const Book& b)
    {
       return author < b.author;
    }
  private:
    std::string author;
};

如果要按其他字段排序，则需要编写自定义比较运算符：

class Book
{
  std::string title;
  friend bool order_by_title(const Book& a, const Book& b);
};

bool order_by_title(const& Book a, const Book& b)
{
  return a.title < b.title;
}

std::vector<Book> library;
//...
std::sort(library.begin(), library.end(), order_by_title);

按字母顺序排序书名

2 个答案: