struct Person{
char name[64];
int age;
};
typedef struct _PERSON{
char name[64];
int age;
}Person;
注意:定义结构体类型时不要直接给成员赋值,结构体只是一个类型,编译器还没有为其分配空间,只有根据其类型定义变量时,才分配空间,有空间后才能赋值。
struct Person{
char name[64];
int age;
}p1; //定义类型同时定义变量
struct{
char name[64];
int age;
}p2; //定义类型同时定义变量
struct Person p3; //通过类型直接定义
struct Person{
char name[64];
int age;
}p1 = {"john",10}; //定义类型同时初始化变量
struct{
char name[64];
int age;
}p2 = {"Obama",30}; //定义类型同时初始化变量
struct Person p3 = {"Edward",33}; //通过类型直接定义
struct Person{
char name[64];
int age;
};
void test(){
//在栈上分配空间
struct Person p1;
strcpy(p1.name, "John");
p1.age = 30;
//如果是普通变量,通过点运算符操作结构体成员
printf("Name:%s Age:%d\n", p1.name, p1.age);
//在堆上分配空间
struct Person* p2 = (struct Person*)malloc(sizeof(struct Person));
strcpy(p2->name, "Obama");
p2->age = 33;
//如果是指针变量,通过->操作结构体成员
printf("Name:%s Age:%d\n", p2->name, p2->age);
}
1)赋值基本概念
相同的两个结构体变量可以相互赋值,把一个结构体变量的值拷贝给另一个结构体,这两个变量还是两个独立的变量。
struct Person{
char name[64];
int age;
};
void test(){
//在栈上分配空间
struct Person p1 = { "John" , 30};
struct Person p2 = { "Obama", 33 };
printf("Name:%s Age:%d\n", p1.name, p1.age);
printf("Name:%s Age:%d\n", p2.name, p2.age);
//将p2的值赋值给p1
p1 = p2;
printf("Name:%s Age:%d\n", p1.name, p1.age);
printf("Name:%s Age:%d\n", p2.name, p2.age);
}
2)深拷贝和浅拷贝
//一个老师有N个学生
typedef struct _TEACHER{
char* name;
}Teacher;
void test(){
Teacher t1;
t1.name = malloc(64);
strcpy(t1.name , "John");
Teacher t2;
t2 = t1;
//对手动开辟的内存,需要手动拷贝
t2.name = malloc(64);
strcpy(t2.name, t1.name);
if (t1.name != NULL){
free(t1.name);
t1.name = NULL;
}
if (t2.name != NULL){
free(t2.name);
t1.name = NULL;
}
}
struct Person{
char name[64];
int age;
};
void test(){
//在栈上分配空间
struct Person p1[3] = {
{ "John", 30 },
{ "Obama", 33 },
{ "Edward", 25}
};
struct Person p2[3] = { "John", 30, "Obama", 33, "Edward", 25 };
for (int i = 0; i < 3;i ++){
printf("Name:%s Age:%d\n",p1[i].name,p1[i].age);
}
printf("-----------------\n");
for (int i = 0; i < 3; i++){
printf("Name:%s Age:%d\n", p2[i].name, p2[i].age);
}
printf("-----------------\n");
//在堆上分配结构体数组
struct Person* p3 = (struct Person*)malloc(sizeof(struct Person) * 3);
for (int i = 0; i < 3;i++){
sprintf(p3[i].name, "Name_%d", i + 1);
p3[i].age = 20 + i;
}
for (int i = 0; i < 3; i++){
printf("Name:%s Age:%d\n", p3[i].name, p3[i].age);
}
}
struct Person{
char* name;
int age;
};
void allocate_memory(struct Person** person){
if (person == NULL){
return;
}
struct Person* temp = (struct Person*)malloc(sizeof(struct Person));
if (temp == NULL){
return;
}
//给name指针分配内存
temp->name = (char*)malloc(sizeof(char)* 64);
strcpy(temp->name, "John");
temp->age = 100;
*person = temp;
}
void print_person(struct Person* person){
printf("Name:%s Age:%d\n",person->name,person->age);
}
void free_memory(struct Person** person){
if (person == NULL){
return;
}
struct Person* temp = *person;
if (temp->name != NULL){
free(temp->name);
temp->name = NULL;
}
free(temp);
}
void test(){
struct Person* p = NULL;
allocate_memory(&p);
print_person(p);
free_memory(&p);
}
//一个老师有N个学生
typedef struct _TEACHER{
char name[64];
char** students;
}Teacher;
void create_teacher(Teacher** teacher,int n,int m){
if (teacher == NULL){
return;
}
//创建老师数组
Teacher* teachers = (Teacher*)malloc(sizeof(Teacher)* n);
if (teachers == NULL){
return;
}
//给每一个老师分配学生
int num = 0;
for (int i = 0; i < n; i ++){
sprintf(teachers[i].name, "老师_%d", i + 1);
teachers[i].students = (char**)malloc(sizeof(char*) * m);
for (int j = 0; j < m;j++){
teachers[i].students[j] = malloc(64);
sprintf(teachers[i].students[j], "学生_%d", num + 1);
num++;
}
}
*teacher = teachers;
}
void print_teacher(Teacher* teacher,int n,int m){
for (int i = 0; i < n; i ++){
printf("%s:\n", teacher[i].name);
for (int j = 0; j < m;j++){
printf(" %s",teacher[i].students[j]);
}
printf("\n");
}
}
void free_memory(Teacher** teacher,int n,int m){
if (teacher == NULL){
return;
}
Teacher* temp = *teacher;
for (int i = 0; i < n; i ++){
for (int j = 0; j < m;j ++){
free(temp[i].students[j]);
temp[i].students[j] = NULL;
}
free(temp[i].students);
temp[i].students = NULL;
}
free(temp);
}
void test(){
Teacher* p = NULL;
create_teacher(&p,2,3);
print_teacher(p, 2, 3);
free_memory(&p,2,3);
}