c语言结构体

定义结构体变量

struct Student{    char *name;    int age;    int score;};void main(){    struct Student st1;    system("pause");}

#include <stdlib.h>#include <string.h>#include <stdio.h>typedef struct Student{    char *name;    int age;    int score;}student;void main(){    student st1;    system("pause");}

struct Student{    char *name;    int age;    int score;}st2;void main(){    system("pause");}

struct {    char *name;    int age;    int score;}st2;

初始化变量

//方法一typedef struct Teacher{    char name[64];    int age ;    int id;}Teacher;Teacher  t3 = {"aaaa", 31, 01};//方法二struct Student2{    char name[64];    int aga ;}s5 = {"names", 21};//方法三struct {    char name[64];    int aga ;}s6 = {"names", 21};

访问成员

使用.运算符访问结构体成员
使用->运算符访问结构体成员

在定义了 library 和 library2 两个结构体后，若想要访问其内部成员，应该使用结构体成员运算符点(.)就可以，例如：

library.value = 9;  library.title

如何使用结构体指针访问结构体成员
1、结构体指针的定义和初始化

     struct book *it;     it = &library；

2、使用结构体指针it访问结构体成员变量

     it->value = 9;     it->title;

结构体变量作函数参数 VS 结构体指针作函数参数

void  copyTeacher(Teacher to, Teacher from ){    to = from;  }//值传递void  copyTeacher02(Teacher *to, Teacher *from ){    //(*to) = (*from);    *to = *from;}void main(){    Teacher  t1 = {"aaaa", 32, 02};    Teacher  t2;    Teacher  t3;    memset(&t3, 0, sizeof(t3));    t2 = t1; //=号操作下 编译器的行为    //编译器给我们提供 简单 =号 赋值操作 。。。我们要顺从    printf("t2.name:%s \n", t2.name);    printf("t2.age:%d \n", t2.age);    copyTeacher(t3, t1);    printf("copyTeacher() after \n");    printf("t3.name:%s \n", t3.name);    printf("t3.age:%d \n", t3.age);    printf("hello...\n");    copyTeacher02(&t3, &t1);    printf("copyTeacher02() after \n");    printf("t3.name:%s \n", t3.name);    printf("t3.age:%d \n", t3.age);    printf("hello...\n");    system("pause");    return ;}

t2.name:aaaat2.age:32copyTeacher() aftert3.name:t3.age:0hello...copyTeacher02() aftert3.name:aaaat3.age:32hello...请按任意键继续. . .

结构体指针的输入输出模型

#define  _CRT_SECURE_NO_WARNINGS #include <stdlib.h>#include <string.h>#include <stdio.h>typedef struct Teacher{    char name[64];    int age ;    int id;}Teacher;void printTeacher(Teacher *array, int num){    int i = 0;    for (i=0; i<num; i++)    {        printf("age:%d \n", array[i].age);    }}void sortTeacer(Teacher *array, int num){    int     i,j;    Teacher tmp;    for (i=0; i<num; i++)    {        for (j=i+1; j<num; j++)        {            if (array[i].age > array[j].age)            {                tmp = array[i];  //=号操作  赋值操作                array[i] = array[j];                array[j] = tmp;            }        }    }}// 结构体数组 3  输入老师的年龄，排序void main(){    int         i = 0;    Teacher     Array[3];  //在stack 分配内存    int         num = 3;    for (i=0; i<num; i++)    {        printf("\nplease enter age:");        scanf("%d", &(Array[i].age) );    }    //打印老师年龄//  for (i=0; i<num; i++)//  {//      printf("age:%d \n", Array[i].age);//  }    printTeacher(Array, num);    sortTeacer(Array, num);    printf("排序之后\n");    printTeacher(Array, num);    printf("hello...\n");    system("pause");    return ;}Teacher * createTeacher(int num){    Teacher * tmp = NULL;    tmp = (Teacher *)malloc(sizeof(Teacher) * num); //  Teacher     Array[3]    if (tmp == NULL)    {        return NULL;    }    return tmp; //}void FreeTeacher(Teacher *p){    if (p != NULL)    {        free(p);    }}void main233(){    int         i = 0;    //Teacher       Array[3];  //在stack 分配内存    int         num = 3;    Teacher *pArray = NULL;    pArray = createTeacher(num);    for (i=0; i<num; i++)    {        printf("\nplease enter age:");        scanf("%d", & (pArray[i].age) );    }    //打印老师年龄    //  for (i=0; i<num; i++)    //  {    //      printf("age:%d \n", Array[i].age);    //  }    printTeacher(pArray, num);    sortTeacer(pArray, num);    printf("排序之后\n");    printTeacher(pArray, num);    FreeTeacher(pArray);    printf("hello...\n");    system("pause");    return ;}

高级一点的输出模型

int createTeacher02(Teacher **pT, int num)

就是把简单输出模型的返回值改为int类型，将在堆空间分配的内存从函数参数用二级指针甩出来。

//修改如下int createTeacher222(Teacher **pT, int num){    Teacher * tmp = NULL;    tmp = (Teacher *)malloc(sizeof(Teacher) * num); //  Teacher     Array[3]    if (tmp == NULL)    {        return NULL;    }    *pT = tmp;    return 0; //}void main(){    int         i = 0;    //Teacher       Array[3];  //在stack 分配内存    int         num = 3;    Teacher *pArray = NULL;    createTeacher222(&pArray,num);    for (i = 0; i<num; i++)    {        printf("\nplease enter age:");        scanf("%d", &(pArray[i].age));    }    printTeacher(pArray, num);    sortTeacer(pArray, num);    printf("排序之后\n");    printTeacher(pArray, num);    FreeTeacher(pArray);    printf("hello...\n");    system("pause");    return;}

结构体中套一级指针

#define  _CRT_SECURE_NO_WARNINGS #include <stdlib.h>#include <string.h>#include <stdio.h>typedef struct _student{    char name[64];    char *alias;    int age;}student;int createStudent(student **ptr,int count){    int ret = 0;    int i = 0;    student * tmp = NULL;    tmp = (student*)malloc(count*sizeof(student));//申请结构体变量所需的内存空间，相当于一个结构体数组    if (tmp == NULL)//申请失败    {        return -1;    }    memset(tmp, 0, count*sizeof(student));//初始化新分配到的内存空间    for (i = 0; i < count;i++){//逐个对结构体变量中的一级指针成员申请空间，否则之前申请的空间只是一个指针变量，这个指针变量并没有实际的内存空间        tmp[i].alias = (char *)malloc(64);        if (NULL == tmp[i].alias){            return -1;        }    }    *ptr = tmp;//通过函数参数甩出内存空间    return ret;}int freeStudent(student **ptr,int count){    int ret = 0;    int  i = 0;    student * tmp = NULL;    if (ptr == NULL){        return -1;    }    tmp = *ptr;    for (i = 0; i < count; i++)    {        if (tmp[i].alias != NULL){            free(tmp[i].alias);            tmp[i].alias = NULL;        }    }    free(tmp);    *ptr = NULL;    return ret;}void printStudent(student *ptr, int count){    int i = 0;    for (i = 0; i < count; i++){//逐个打印结构体变量的age成员        printf("age:%d\n", ptr[i].age);    }}//依据年龄排序void sortStudent(student *ptr, int count){    int i = 0, j = 0;    student tmp;    for (i = 0; i < count;i++)    {        for (j = i + 1; j < count; j++)        {            if (ptr[i].age > ptr[j].age)            {                tmp = ptr[i];                ptr[i] = ptr[j];                ptr[j] = tmp;            }        }    }}int  main(){    int ret = 0;    student *pStudent = NULL;    int num = 3,i = 0;    ret = createStudent(&pStudent, num);//创造一个结构体数组    if (-1 == ret){        return -1;    }    for (i = 0; i < num; i++)//依次输入结构体成员变量的值    {        printf("\nplease enter age:");        scanf("%d", &(pStudent[i].age));        printf("\nplease enter name:");        scanf("%s", pStudent[i].name); //向指针所指的内存空间copy数据        printf("\nplease enter alias:");        scanf("%s", pStudent[i].alias);  //向指针所指的内存空间copy数据    }    printf("排序之前\n");    printStudent(pStudent, num);    sortStudent(pStudent, num);    printf("排序之后\n");    printStudent(pStudent, num);    freeStudent(&pStudent,num);    system("pause");    return ret;}

结构体中套二级指针

#define  _CRT_SECURE_NO_WARNINGS #include <stdlib.h>#include <string.h>#include <stdio.h>#define FRIEND_NUM 3typedef struct _student{    char name[64];    char *alias;    char **friends;    int age;}student;int createStudent(student **ptr,int count){    int ret = 0;    int i = 0, j = 0;    student * tmp = NULL;    char **ptmp = NULL;    tmp = (student*)malloc(count*sizeof(student));//申请结构体变量所需的内存空间，相当于一个结构体数组    if (tmp == NULL)//申请失败    {        return -1;    }    memset(tmp, 0, count*sizeof(student));//初始化新分配到的内存空间    for (i = 0; i < count;i++){//逐个对结构体变量中的一级指针成员申请空间，否则之前申请的空间只是一个指针变量，这个指针变量并没有实际的内存空间        /*一级指针内存模型*/        tmp[i].alias = (char *)malloc(64);        if (NULL == tmp[i].alias){            return -1;        }        /*二级指针第三种内存模型*/        ptmp = (char**)malloc(FRIEND_NUM*sizeof(char*));//二级指针指向一个二维数组，第一维是char*        if (ptmp == NULL)        {            return -1;        }        for (j = 0; j < FRIEND_NUM; j++)        {            ptmp[j] = (char*)malloc(64);//第一维的每一个char*指向一个malloc空间        }        tmp[i].friends = ptmp;//将二级指针抛出给已分配好的结构体二级指针成员变量    }    *ptr = tmp;//通过函数参数甩出内存空间    return ret;}int freeStudent(student **ptr,int count){    int ret = 0;    int  i = 0,j = 0;    char ** ptmp = NULL;    student * tmp = NULL;    if (ptr == NULL){        return -1;    }    tmp = *ptr;    for (i = 0; i < count; i++)    {        if (tmp[i].alias != NULL){//释放一级指针            free(tmp[i].alias);            tmp[i].alias = NULL;        }        if (tmp[i].friends != NULL)//释放二级指针        {            ptmp = tmp[i].friends;            for (j = 0; j < FRIEND_NUM; j++)            {                if (ptmp[j] != NULL)                {                    free(ptmp[j]);                    ptmp[j] = NULL;                }            }            free(ptmp);            tmp[i].friends = NULL;//注意ptmp只是一个临时变量，不能修改原结构体成员的值        }    }    free(tmp);    *ptr = NULL;//修改主调函数的一级指针要使用二级指针    return ret;}void printStudent(student *ptr, int count){    int i = 0;    for (i = 0; i < count; i++){//逐个打印结构体变量的age成员        printf("age:%d\n", ptr[i].age);    }}//依据年龄排序void sortStudent(student *ptr, int count){    int i = 0, j = 0;    student tmp;    for (i = 0; i < count;i++)    {        for (j = i + 1; j < count; j++)        {            if (ptr[i].age > ptr[j].age)            {                tmp = ptr[i];                ptr[i] = ptr[j];                ptr[j] = tmp;            }        }    }}int  main(){    int ret = 0;    student *pStudent = NULL;    int num = 3,i = 0,j = 0;    ret = createStudent(&pStudent, num);//创造一个结构体数组    if (-1 == ret){        return -1;    }    for (i = 0; i < num; i++)//依次输入结构体成员变量的值    {        printf("\nplease enter age:");        scanf("%d", &(pStudent[i].age));        //printf("\nplease enter name:");        //scanf("%s", pStudent[i].name); //向指针所指的内存空间copy数据        //printf("\nplease enter alias:");        //scanf("%s", pStudent[i].alias);  //向指针所指的内存空间copy数据        for (j = 0; j < FRIEND_NUM; j++)//给二级指针指向的内存空间的一级指针指向的内存空间赋值        {            printf("please enter student name:");            scanf("%s", pStudent[i].friends[j]);        }    }    printf("排序之前\n");    printStudent(pStudent, num);    sortStudent(pStudent, num);    printf("排序之后\n");    printStudent(pStudent, num);    freeStudent(&pStudent,num);    system("pause");    return ret;}

结构体的深浅拷贝

编译器的等号操作只会把指针变量的值拷贝，不会把指针变量指向的内存空间拷贝过去，就是所谓的浅拷贝（只进行简单的值拷贝操作）。
memcpy函数也是浅拷贝
结构体里面出现一级或者二级指针会出现浅拷贝

#define _CRT_SECURE_NO_WARNINGS#include <stdio.h>#include <stdlib.h>#include <string.h>typedef struct __teacher{    char name[64];    int age;    char *alias;}Teacher;void copyTeacher(Teacher *to,Teacher *from){    //*to = *from;//浅拷贝    memcpy(to, from, sizeof(Teacher));//浅拷贝}int main(void){    Teacher t1;    Teacher t2;    strcpy(t1.name,"name1");    t1.alias = (char*)malloc(100);    strcpy(t1.alias,"ssss");    copyTeacher(&t2, &t1);    if (t1.alias != NULL)    {        free(t1.alias);        t1.alias = NULL;    }    if (t2.alias != NULL)//运行到这里由于前面已经free，这里二次free会出错    {        free(t2.alias);        t2.alias = NULL;    }    system("PAUSE");    return 1;}

//要进行深拷贝只能是显示的分配内存，即在堆里面再开辟一块内存给另一个结构体的指针成员使用，所以可以进行二次释放。主要代码如下：void copyTeacher(Teacher *to,Teacher *from){    *to = *from;    to->alias = (char *)malloc(100);    strcpy(to->alias,from->alias);    //memcpy(to, from, sizeof(Teacher));}