结构体的基本操作
2022-10-08 本文已影响0人
arkliu
结构体定义和初始化
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
// 1. 结构体类型的定义
//struct关键字
//struct Teacher合在一起才是类型
struct Teacher
{
char name[50];
int age;
};
//3. 定义类型的同时，定义变量
struct Student
{
char name[50];
int age;
}st1, st2;
// 5. 通过typedef改类型名字
typedef struct People {
char name[50];
int age;
} People;
int main() {
// 2. 结构体变量的声明
struct Teacher teacher;
// 4.结构体变量初始化
// 4.1定义变量时候直接初始化，通过{}
struct Teacher teacher1 = {"zhangsan", 22};
printf("name = %s age = %d\n", teacher1.name, teacher1.age); //name = zhangsan age = 22
People people;
strcpy(people.name, "wangwu");
people.age = 34;
printf("name = %s age = %d\n", people.name, people.age);
struct Teacher * teacher2 = malloc(sizeof(struct Teacher));
strcpy(teacher2->name, "wangwu");
teacher2->age = 34;
printf("name = %s age = %d\n", teacher2->name, teacher2->age);
}
结构体变量相互赋值
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
typedef struct People {
char name[50];
int age;
} People;
void copyPeople(People *dest, People source) {
dest->age = source.age;
strcpy(dest->name,source.name);
}
int main() {
People people = {"李四", 23};
//相同类型的两个结构体变量可以相互赋值
//把people成员变量内存的值拷贝到people2成员变量的内存
People people2 = people;
printf("name = %s age = %d\n", people2.name, people2.age);
People p3;
memset(&p3, 0, sizeof(p3));
copyPeople(&p3, people);
printf("name = %s age = %d\n", p3.name, p3.age);
}
结构体数组
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
typedef struct People {
char name[50];
int age;
} People;
int main() {
People p[3] = {
{"abc", 22},
{"def", 33},
{"ghi", 44}
};
//静态
People p2[3] = {"abc", 22,"def", 33,"ghi", 44};
for (size_t i = 0; i < 3; i++)
{
printf("name = %s age = %d\n", p2[i].name, p2[i].age);
}
//动态
People * p3 = malloc(3 * sizeof(People));
char buf[128];
for (size_t i = 0; i < 3; i++)
{
sprintf(buf, "name%d%d", i, i);
strcpy(p3[i].name, buf);
p3[i].age = i;
}
for (size_t i = 0; i < 3; i++)
{
printf("name = %s age = %d\n", p3[i].name, p3[i].age);
}
if (p3 != NULL)
{
free(p3);
p3 = NULL;
}
}
结构体嵌套一级指针
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
typedef struct People {
char * name;
int age;
} People;
int main() {
People p1;
p1.age = 22;
p1.name = (char *)malloc(30 * sizeof(char));
strcpy(p1.name, "张三");
printf("p1 name = %s age = %d\n", p1.name, p1.age); //p1 name = 张三 age = 22
if (p1.name != NULL)
{
free(p1.name);
p1.name = NULL;
}
People * p2;
p2 = (People *)malloc(sizeof(People));
p2->age = 33;
p2->name = (char *)malloc(30 * sizeof(char));
strcpy(p2->name, "李四");
printf("p2 name = %s age = %d\n", p2->name, p2->age);
if (p2->name != NULL)
{
free(p2->name);
p2->name = NULL;
}
if (p2 != NULL)
{
free(p2);
p2 = NULL;
}
People * p3;
p3 = (People *)malloc(sizeof(People) * 3);
char buf[128];
for (size_t i = 0; i < 3; i++)
{
p3[i].age = i;
p3[i].name = malloc(sizeof(char) * 30);
sprintf(buf, "name %d %d", i, i);
strcpy(p3[i].name, buf);
}
for (size_t i = 0; i < 3; i++)
{
printf("p3 name = %s age = %d\n", p3[i].name, p3[i].age);
}
for (size_t i = 0; i < 3; i++)
{
if (p3[i].name != NULL)
{
free(p3[i].name);
p3[i].name = NULL;
}
}
if (p3 != NULL)
{
free(p3);
p3 = NULL;
}
}
结构体嵌套二级指针
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#define STU_SIZE 3
//一个老师对应多个学生
typedef struct Teacher {
char ** stu;
} Teacher;
int main() {
// init
Teacher t1;
t1.stu = (char **)malloc(sizeof(char *) * STU_SIZE);
char buf[128];
for (size_t i = 0; i < STU_SIZE; i++)
{
t1.stu[i] = (char *)malloc(sizeof(char) * 30);
sprintf(buf, "name %d%d", i,i);
strcpy(t1.stu[i], buf);
}
// print
for (size_t i = 0; i < STU_SIZE; i++)
{
printf("name = %s\n", t1.stu[i]);
}
//free
for (size_t i = 0; i < STU_SIZE; i++)
{
if (t1.stu[i] != NULL)
{
free(t1.stu[i]);
t1.stu[i] = NULL;
}
}
if (t1.stu != NULL)
{
free(t1.stu);
t1.stu = NULL;
}
// init
Teacher * t2;
t2 = (Teacher *)malloc(sizeof(Teacher));
t2->stu = (char **)malloc(sizeof(char *) * STU_SIZE);
for (size_t i = 0; i < STU_SIZE; i++)
{
t2->stu[i] = (char *)malloc(sizeof(char) * 30);
sprintf(buf, "name %d%d", i,i);
strcpy(t2->stu[i], buf);
}
// print
for (size_t i = 0; i < STU_SIZE; i++)
{
printf("name = %s\n", t2->stu[i]);
}
// free
for (size_t i = 0; i < STU_SIZE; i++)
{
if (t2->stu[i] != NULL)
{
free(t2->stu[i]);
t2->stu[i] = NULL;
}
}
if (t2->stu != NULL)
{
free(t2->stu);
t2->stu = NULL;
}
if (t2 != NULL)
{
free(t2);
t2 = NULL;
}
return 0;
}
结构体偏移量
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#define STU_SIZE 3
//结构体类型定义下来，内部的成员变量的内存布局已经确定
typedef struct Teacher {
char name[64]; // 64
int age; // 4
int id; // 4
} Teacher;
int main() {
Teacher t1;
Teacher * t2 = NULL;
t2 = &t1;
int n1 = (int)(&t2->age) - (int)t2; // 相对于结构体首地址
printf("n1 = %d\n", n1); // n1 = 64
return 0;
}
联合体
将几种不同类型的变量存放到同一段内存中，这种数据结构称为联合体
- 联合体重所有成员使用的是内存中的相同位置
- 联合的长度是它最长成员的长度
- 联合变量的定义方式和结构体相同，只要将关键字换成union
- 联合变量初始化必须是联合的第一个成员类型值
#include <stdio.h>
int main() {
union TestUnion
{
int a;
float b;
char c;
} un={10};
printf("a: %d b:%f c: %c", un.a, un.b, un.c);
un.b = 8.8f;
printf("a: %d b:%f c: %c", un.a, un.b, un.c);
return 0;
}
