C++ 数据结构
C/C++ 数组允许您定义组合多个同类数据项的变量，但结构是另一种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，假设您想跟踪图书馆中的书籍。您可能想要跟踪每本书的以下属性 -
- 标题
- 作者
- 主题
- 图书编号
定义结构
要定义结构，必须使用 struct 语句。struct 语句为您的程序定义了一种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];
结构体标签是可选的，每个成员定义都是普通的变量定义，如int i；或浮动 f；或任何其他有效的变量定义。在结构定义的末尾，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。这是声明 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
要访问结构体的任何成员，我们使用成员访问运算符 (.)。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;
}
当上面的代码被编译并执行时，它会产生以下结果 -
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
结构体作为函数参数
您可以将结构作为函数参数传递，其方式与传递任何其他变量或指针非常相似。您可以按照与上例中访问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;
}
当上面的代码被编译并执行时，它会产生以下结果 -
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
结构体指针
您可以以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，您可以将结构体变量的地址存储在上面定义的指针变量中。要查找结构体变量的地址，请将 & 运算符放在结构体名称之前，如下所示 -
struct_pointer = &Book1;
要使用指向该结构的指针访问该结构的成员，必须使用 -> 运算符，如下所示 -
struct_pointer->title;
让我们使用结构体指针重写上面的示例，希望这对您来说很容易理解这个概念 -
#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;
}
当上面的代码被编译并执行时，它会产生以下结果 -
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“别名”您创建的类型。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，如下所示 -
typedef long int *pint32; pint32 x, y, z;
x、y 和 z 都是指向长整型的指针。