结构体中包含二级指针案例

给出如下结构体，要求全部在堆区开辟空间。有多个老师，每个老师有多个学生。

typedef struct
{
	char *name;//老师
	int stu_num;//学生数
	char **stu_arr;//学生名字
}TEACHER;

需要注意以下问题：

1. 此问题使用双层循环即可解决。
2. 外层循环处理这三个成员变量：给name开辟空间；给stu_num赋值；给stu_arr开辟5个连续的保存一级地址地char**类型的空间。即给成员变量赋值。
3. 在内层循环中使用stu_arr5个char*类型的空间开辟，每个均开辟5个char*类型的空间，再给他们赋值。当然，这个过程(内层循环)要执行25次。即给二级地址中引用的一级地址开辟空间并赋值。

#define _CRT_SECURE_NO_WARNINGS
#include<stdio.h>
#include<stdlib.h>
#include<string.h>
typedef struct
{
	char *name;
	int stu_num;
	char **stu_arr;
}TEACHER;

int main(int argc, char *argv[])
{
	TEACHER **teachers = (TEACHER **)calloc(5, sizeof(TEACHER));
	for (int i = 0; i < 5; i++)
	{
		//*name
		teachers[i] = (TEACHER*)calloc(1, sizeof(TEACHER));
		teachers[i]->name = (char *)calloc(32, sizeof(char));
		strcpy(teachers[i]->name, "lao_shi");
		printf("%s\n", teachers[i]->name);
		
		//stu_num
		teachers[i]->stu_num = 3;
		printf("%d\n", teachers[i]->stu_num);
		
		//**stu_arr 
		teachers[i]->stu_arr = (char **)calloc(5, sizeof(char *));
		printf("%p\n", teachers[i]->stu_arr);
		
		for (int j = 0; j < 5; j++)
		{
			//*stu_arr
			teachers[i]->stu_arr[j] = (char *)calloc(teachers[i]->stu_num, 128 * sizeof(char));
			strcpy(teachers[i]->stu_arr[j], "xiao_ming");
			printf("%s\n", teachers[i]->stu_arr[j]);
		}
	}

	//释放
	for (int i = 0; i < 5; i++)
		for (int j = 0; j < 5; j++)
			if (teachers[i]->stu_arr[j]) free(teachers[i]->stu_arr[j]), teachers[i]->stu_arr[j] = NULL;

	for (int i = 0; i < 5; i++) if (teachers[i]) free(teachers[i]), teachers[i] = NULL;

	if (teachers) free(teachers), teachers = NULL;
	
	
	system("pause");
	return 0;
}