c语言笔记二级指针,malloc_malloc二级指针-优快云博客

本文链接：https://blog.youkuaiyun.com/hhyygg2009/article/details/90765624

本文详细介绍了使用C语言如何通过结构体和动态内存分配来创建和释放教师及学生信息的数据结构。具体包括定义Teacher结构体，内含指向姓名、年龄和学生姓名的指针；实现creatTeacher函数，用于创建指定数量的Teacher实例并为每个实例分配内存；实现freeTeacher函数，用于释放所有Teacher实例及其关联的学生姓名内存。

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#include <stdio.h>
#include <stdlib.h>
#include <string.h>
typedef struct
{
	char *tName;
	int age;
	char **stuName;
}Teacher;
int creatTeacher(Teacher **teacher, int num)
{
	int i, j;
	*teacher = (Teacher *)malloc(sizeof(Teacher)*num);
	for (i = 0; i < num; i++)
	{
		(*teacher)[i].tName = (char*)malloc(sizeof(char) * 20);     //给num个老师的tname开辟内存空间
		(*teacher)[i].stuName = (char**)malloc(sizeof(char*) * 3);   //开辟三个指向char*的内存空间
		for (j = 0; j < 3; j++)
		{
			(*teacher)[i].stuName[j] = (char*)malloc(sizeof(char) * 20);//每个char*分配20个字符
		}
	}
	return 0;
}
int freeTeacher(Teacher **teacher, int num)
{
	int i, j;
	char **p;
	for (i = 0; i < num; i++)
	{
		if ((*teacher)[i].stuName != NULL)
		{
			p = (*teacher)[i].stuName;
			for (j = 0; j < 3; j++)
			{
				if (p[j] != NULL)
					free(p[j]);
			}
			free(p);
			(*teacher)[i].stuName = NULL;
		}

	}

	free(*teacher);
	*teacher = NULL;
	return 0;
}
int main()
{
	Teacher *t = NULL;
	int i, j,x;
		x = 0;
	creatTeacher(&t, 2);
	char tName1[20] = { "abcd" };
	char stuName[][20] = { "11","22" ,"33","111","222","333" };
	for (j = 0; j < 2; j++)
	{
		t[j].tName = tName1;
		t[j].age = 30;
		for (i = 0; i < 3; i++,x++) {
			
			//t[j].stuName[i] = stuName[x];//
			strcpy(t[j].stuName[i], stuName[x]);
		}
	}
	freeTeacher(&t, 2);
	system("pause");
}