10结构体

结构类型定义的典型格式：

struct <结构名>  { <成员列表> };

例子：

 struct student

 {   int num;

     char name[20];

     char sex;

     float score;

 };

 

结构变量声明的典型格式：

<结构名>   <变量列表> ;

例子：

  student  stud1, stud2,

           *sptr, stu[20];

 

同时进行结构类型定义和结构变量声明

例子：

  struct student

 {   int num;

     char name[20];

     char sex;

     float score;

 } stud1, stud2, *sptr;

结构类型student可用于声明其它变量

 

 

 

用无名结构类型进行结构变量声明

例子：

  struct

 {   int num;

     char name[20];

     char sex;

     float score;

 } stud1, stud2, *sptr;

无名结构类型无法用于声明其它变量

 

结构的定义可以嵌套

例子：

  struct date {int year; int month;

               int day; };

 

struct people {int num; char sex;

               char name[20];  

               date birthday;

              };

people  wang;

 

注意：

结构定义时不能定义本类型的成员

例子：

  struct fdate

   {int year; int month; int day;

    fdate *fptr;

    fdate birthday;

 };

 

结构变量的初始化

例子：

  student stud5 =

{ 102, "Li Xiaoming", 'M', 92 };

  student class[2] = {

{ 102, "Li Xiaoming", 'M', 92 },

{ 105, “Wang Ming", ‘F', 88 } };

 

结构变量的使用

1.同类型结构变量可直接赋值，如stud1 = stud2;

2.用圆点运算符 . 和箭头运算符 -> 对结构的成员进行存取，如

printf( "%s", stud1.name );

wang.birthday.year = 1986;

sptr = &stud1;

  printf( "%s", sptr->name );

    （sptr->name 等价于 (*sptr ).name ）

 

 

结构与函数

结构成员可以作为函数的实在参数

假设有如下函数原型定义：

   void f1(int);

   void f2(float);

   void f3(char *);

   void f4(int *)；

   void f5(float *);

声明结构变量：

   struct student stud;

 

下面的函数调用是合法的：

 f1(stud.num);   //传递stud.num

 f1(stud.name[2]);

 f2(stud.score); //传递stud.score的值

 f3(stud.name);

 f3(&stud.name[2])；

 f4(&stud.num)；//传递成员stud.num的地址

 f5(&stud.score)；

 

函数的参数或返回值可以是结构类型

函数原型：

 void f6(student s);

 student f7(student & s);

 student *f8(student * s);

函数调用：

 f6(stud);

 printf( "%s", f7(stud).name );

 printf( "%s", f8(&stud)->name );

 

 

结构与数组

结构成员可以是数组；数组元素可以是结构（结构数组）。如

struct student

{    int num;

      char name[20];

      char sex;

      float score;

}class[5];

 

 

结构与指针

结构成员可以是指针；指针可以指向结构（结构指针），也可以作为结构成员指向本结构。如

   struct fdate

   {int year; int month; int day;

    fdate *fptr;

    student *Sptr;

 };

 student stud, *pStud=&stud;

 (*pStud).num = 101;

 pStud->score = 95;

 

 

枚举

是一种类型，值为标识符（有限集），每个标识符的内部表示是一个整数。枚举类型的定义如

enum weekday {Sun,Mon,Tue,Wed,Thu,Fri,Sat};

枚举常量：枚举类型定义中的标识符，与一般符号常量类似，但可自动定值，起始值从 0 开始，递增值为 1

可以用 = 为枚举常量定值

枚举类型定义中的标识符必须唯一

枚举变量声明：与一般变量相同

枚举变量只能被赋予相应的枚举常量

示例：

enum weekday1 {Sun=1,Mon,Tue,Wed,Thu,Fri,Sat};

enum weekday2 {Sun=1,Mon,Tue=5,Wed,Thu,Fri=10,Sat};

weekday1  day1 ;  weekday2  day2 ;

day1 = Mon;//等价于 day1 = (weekday1)2

day2 = Wed;//等价于 day2 = (weekday2)6

cout<< day1 <<endl<< day2;

 

 

例子一：结构体作为函数的参数

#include <iostream.h>

struct student

{

  int num;

  char name [ 20 ];

  char sex;

  float score;

};

void displayStudentInfo(

                     const student & stud)

 {cout << endl;

  cout << "num = " << stud.num << "\t";

  cout << "name = " << stud.name << "\t";

  cout << "sex = " << stud.sex << "\t";

  cout << "score = "<<stud.score<<endl;

 }

void funCallByValue (student stud)

 {stud.score ++; }

void funCallByReference (student &stud)

 {stud.score ++; } 

void funCallByPointer (student * stud)

 {stud->score ++; }

main()

 {student theStud =

        { 102, "Li Xiaoming", 'M', 92 };

  cout << "Initial information:";

  displayStudentInfo ( theStud ) ;

  funCallByValue ( theStud ) ;

  cout << "\nAfter call by value:";

  displayStudentInfo ( theStud ) ;

  funCallByReference ( theStud ) ;

  cout << "\nAfter call by reference:";

  displayStudentInfo ( theStud ) ;

  funCallByPointer ( & theStud );

  cout << "\nAfter call by pointer:";

  displayStudentInfo ( theStud );

  return 0;

 } 

 

 

例子二：函数以结构体为返回值

#include <iostream.h>

struct student

 {int num;

  char name[20];

  char sex;

  float score;

 };

void displayStudentInfo(

                    const student & stud)

 {cout << endl;

  cout << "num = " << stud.num << "\t";

  cout << "name = " << stud.name << "\t";

  cout << "sex = " << stud.sex << "\t";

  cout << "score = "<< stud.score<< endl;

 }

student getStudent()

 {

  student stud;

  cout << "Please enter the number: ";

  cin >> stud.num;

  cout << "Please enter the name: ";

  cin >> stud.name;

  cout << "Please enter the sex: ";

  cin >> stud.sex;

  cout << "Please enter the score: ";

  cin >> stud.score;

  return stud;

 }

main()

 {

  student theStud = { 102, "Li Xiaoming", 'M', 92 };

 

  cout << "Initial student information:";

  displayStudentInfo(theStud);

 

  theStud = getStudent();

  cout << "\nAfter call getStudent:";

  displayStudentInfo(theStud);

     

  return 0;

 }

 

例子三：将学生记录按学号大小排序

     #include   <iostream.h>

  #define   STUDENT_Num 5

  struct  student

   { int num;

     char name[20];

     char sex;

     float score;

   };

void displayStudentsInfo(              

        const student studs[], int  len)

  {for (int  i = 0; i < len ; i ++ )

    {cout << "num = "

          << studs[ i ].num << "\t";

     cout << "name = "

          << studs[ i ].name << "\t";

     cout << "sex = "

          << studs[ i ].sex << "\t";

     cout << "score = "

          << studs[ i ].score << endl;

        }

  }

void  sortArray(student studs[],int len)

 {for (int pass = 0;

       pass < len - 1;  pass ++ )   

   for ( int  i = pass + 1;

         i <= len - 1;  i ++ )  

    if(studs[pass].num>studs[i].num )

     { student   hold;

                 hold = studs[ pass ];                  

                 studs[ pass ] = studs[ i ];

                 studs[ i ] = hold;

            }

 }

main( )

{student   theClass [STUDENT_Num] =

    { {110, "Zhang Ping", 'M', 45},

      {102, "Li Xiaoming", 'M', 92},

      {153, "Wang Ming", 'M', 52.5},

      {134, "Cheng Ling", 'F', 87},

      {105, "Wang Xiaofang", 'F', 95}}; 

 cout <<"Initial student information:\n";

 displayStudentsInfo(theClass,

                     STUDENT_Num );

 cout << "\nAfter sorting:\n";

 sortArray ( theClass, STUDENT_Num );

 displayStudentsInfo(theClass,

                     STUDENT_Num );

 return 0;

}

 

例子四：结构指针变量的声明和使用

#include <iostream.h>

struct student

 {int num;

  char name[20];

  char sex;

  float score; };

main()

 {student stud =

          {102, "Li Xiaoming", 'M', 92};

  student * pStud = & stud;

  cout<< "num = " << stud.num << "\t";

  cout << "name = " << stud.name << "\t";

  cout << "sex = " << stud.sex << "\t";

  cout << "score = "<< stud.score<< endl;

cout << "Access structure "

         " through pointer and ( . ):\n";

 cout << "num = " << (*pStud).num << "\t";

 cout <<"name = "<<(*pStud).name << "\t";

 cout <<"sex = "<<(*pStud).sex << "\t";

 cout <<"score = "<<(*pStud).score<<endl;

 

 cout<<"Access structure "

       " through pointer and ( -> ):\n";

 cout << "num = " << pStud->num << "\t";

 cout << "name = " << pStud->name << "\t";

 cout << "sex = " << pStud->sex << "\t";

 cout <<"score = "<< pStud->score<< endl;

 return 0;

}