C++ Data Structures
C/C ++数组允许您定义组合相同类型的多个数据项的变量,但structure是另一个用户定义的数据类型,它允许您组合不同类型的数据项。
结构用于表示记录,假设您想要在库中跟踪您的书籍。 您可能希望跟踪每本书的以下属性 -
- Title
- Author
- Subject
- 书名
定义一个结构 (Defining a Structure)
要定义结构,必须使用struct语句。 struct语句为您的程序定义了一个具有多个成员的新数据类型。 struct语句的格式是这样的 -
struct [structure tag] {
member definition;
member definition;
...
member definition;
} [one or more structure variables];
structure tag是可选的,每个成员定义是一个普通的变量定义,例如int i; 或浮动f; 或任何其他有效的变量定义。 在结构定义的最后,在最后一个分号之前,您可以指定一个或多个结构变量,但它是可选的。 以下是您声明Book结构的方式 -
struct Books {
char title[50];
char author[50];
char subject[100];
int book_id;
} book;
访问结构成员 (Accessing Structure Members)
要访问结构的任何成员,我们使用member access operator (.) 。 成员访问运算符被编码为结构变量名称和我们希望访问的结构成员之间的句点。 您可以使用struct关键字来定义结构类型的变量。 以下是解释结构用法的示例 -
#include <iostream>
#include <cstring>
using namespace std;
struct Books {
char title[50];
char author[50];
char subject[100];
int book_id;
};
int main() {
struct Books Book1; // Declare Book1 of type Book
struct Books Book2; // Declare Book2 of type Book
// book 1 specification
strcpy( Book1.title, "Learn C++ Programming");
strcpy( Book1.author, "Chand Miyan");
strcpy( Book1.subject, "C++ Programming");
Book1.book_id = 6495407;
// book 2 specification
strcpy( Book2.title, "Telecom Billing");
strcpy( Book2.author, "Yakit Singha");
strcpy( Book2.subject, "Telecom");
Book2.book_id = 6495700;
// Print Book1 info
cout << "Book 1 title : " << Book1.title <<endl;
cout << "Book 1 author : " << Book1.author <<endl;
cout << "Book 1 subject : " << Book1.subject <<endl;
cout << "Book 1 id : " << Book1.book_id <<endl;
// Print Book2 info
cout << "Book 2 title : " << Book2.title <<endl;
cout << "Book 2 author : " << Book2.author <<endl;
cout << "Book 2 subject : " << Book2.subject <<endl;
cout << "Book 2 id : " << Book2.book_id <<endl;
return 0;
}
编译并执行上述代码时,会产生以下结果 -
Book 1 title : Learn C++ Programming
Book 1 author : Chand Miyan
Book 1 subject : C++ Programming
Book 1 id : 6495407
Book 2 title : Telecom Billing
Book 2 author : Yakit Singha
Book 2 subject : Telecom
Book 2 id : 6495700
作为函数参数的结构 (Structures as Function Arguments)
您可以将结构作为函数参数传递,与传递任何其他变量或指针的方式非常相似。 您将以与上面示例中访问过的方式类似的方式访问结构变量 -
#include <iostream>
#include <cstring>
using namespace std;
void printBook( struct Books book );
struct Books {
char title[50];
char author[50];
char subject[100];
int book_id;
};
int main() {
struct Books Book1; // Declare Book1 of type Book
struct Books Book2; // Declare Book2 of type Book
// book 1 specification
strcpy( Book1.title, "Learn C++ Programming");
strcpy( Book1.author, "Chand Miyan");
strcpy( Book1.subject, "C++ Programming");
Book1.book_id = 6495407;
// book 2 specification
strcpy( Book2.title, "Telecom Billing");
strcpy( Book2.author, "Yakit Singha");
strcpy( Book2.subject, "Telecom");
Book2.book_id = 6495700;
// Print Book1 info
printBook( Book1 );
// Print Book2 info
printBook( Book2 );
return 0;
}
void printBook( struct Books book ) {
cout << "Book title : " << book.title <<endl;
cout << "Book author : " << book.author <<endl;
cout << "Book subject : " << book.subject <<endl;
cout << "Book id : " << book.book_id <<endl;
}
编译并执行上述代码时,会产生以下结果 -
Book title : Learn C++ Programming
Book author : Chand Miyan
Book subject : C++ Programming
Book id : 6495407
Book title : Telecom Billing
Book author : Yakit Singha
Book subject : Telecom
Book id : 6495700
指向结构的指针
您可以按照与定义指向任何其他变量的指针非常相似的方式定义指向结构的指针,如下所示 -
struct Books *struct_pointer;
现在,您可以将结构变量的地址存储在上面定义的指针变量中。 要查找结构变量的地址,请将&运算符放在结构名称之前,如下所示 -
struct_pointer = &Book1;
要使用指向该结构的指针访问结构的成员,必须使用 - >运算符,如下所示 -
struct_pointer->title;
让我们用结构指针重新编写上面的例子,希望这对你来说很容易理解 -
#include <iostream>
#include <cstring>
using namespace std;
void printBook( struct Books *book );
struct Books {
char title[50];
char author[50];
char subject[100];
int book_id;
};
int main() {
struct Books Book1; // Declare Book1 of type Book
struct Books Book2; // Declare Book2 of type Book
// Book 1 specification
strcpy( Book1.title, "Learn C++ Programming");
strcpy( Book1.author, "Chand Miyan");
strcpy( Book1.subject, "C++ Programming");
Book1.book_id = 6495407;
// Book 2 specification
strcpy( Book2.title, "Telecom Billing");
strcpy( Book2.author, "Yakit Singha");
strcpy( Book2.subject, "Telecom");
Book2.book_id = 6495700;
// Print Book1 info, passing address of structure
printBook( &Book1 );
// Print Book1 info, passing address of structure
printBook( &Book2 );
return 0;
}
// This function accept pointer to structure as parameter.
void printBook( struct Books *book ) {
cout << "Book title : " << book->title <<endl;
cout << "Book author : " << book->author <<endl;
cout << "Book subject : " << book->subject <<endl;
cout << "Book id : " << book->book_id <<endl;
}
编译并执行上述代码时,会产生以下结果 -
Book title : Learn C++ Programming
Book author : Chand Miyan
Book subject : C++ Programming
Book id : 6495407
Book title : Telecom Billing
Book author : Yakit Singha
Book subject : Telecom
Book id : 6495700
typedef关键字
有一种更简单的方法来定义结构,或者您可以“创建”别名类型。 例如 -
typedef struct {
char title[50];
char author[50];
char subject[100];
int book_id;
} Books;
现在,您可以直接使用Books来定义Books类型的变量,而无需使用struct关键字。 以下是示例 -
Books Book1, Book2;
您可以对非结构使用typedef关键字以及以下 -
typedef long int *pint32;
pint32 x, y, z;
x,y和z都是指向long int的指针。