一级指针的开辟空间和释放资源的两种方法

╰半橙微兮° 2022-05-30 22:27 189阅读 0赞

\#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 printArray(Teacher \*array, int num)  
\{  
for (int i = 0; i < num; i++)  
\{  
printf("Array\[i\]:%d\\n", array\[i\].age);  
\}  
\}  
  
  
void sortArray(Teacher \*array, int num)  
\{  
Teacher tmp;  
for (int i = 0; i < num; i++)  
\{  
for (int j = i + 1; j < num; j++)  
\{  
if (array\[i\].age>array\[j\].age)//从小到大  
\{  
tmp = array\[i\];  
array\[i\] = array\[j\];  
array\[j\] = tmp;  
\}  
\}  
\}  
\}  
  
  
//开辟空间 方法一 return方法  
Teacher \*creatTeacher(int num)  
\{  
Teacher \*tmp = NULL;  
tmp = (Teacher \*)malloc(num \* sizeof(Teacher));  
if (tmp == NULL)  
\{  
return NULL;  
\}  
memset(tmp, 0, sizeof(tmp));//防就止产生野指针 因为能看到没有这句话，返回的tmp修改实参，有乱指的情况，加上就避免这个问题  
return tmp;  
\}  
//开辟空间 方法二 高一级指针（形参）来开辟空间(改变实参的值)  
int  creatTeacher01(Teacher \*\*tmp1, int num)  
\{  
int ret = 0;  
Teacher \*tmp = NULL;  
tmp = (Teacher \*)malloc(num \* sizeof(Teacher));  
if (tmp == NULL)  
\{  
ret = -1;  
printf("func err:%d tmp == NULL\\n", ret);  
return ret;  
\}  
memset(tmp, 0, sizeof(tmp));//防就止产生野指针 因为能看到没有这句话，返回的tmp修改实参，有乱指的情况，加上就避免这个问题  
//\*souce = tmpsource; 用二级指针形参改变一级指针实参  
\*tmp1 = tmp;//指针的间接赋值  
return ret;  
\}  
  
  
//释放一级指针  方法1  
void Free\_Teacher(Teacher \*p)  
\{  
if (p != NULL)  
\{  
free(p);  
\}  
\}  
  
  
//释放一级指针  方法2：让实参一级指针释放资源，采用高一级指针(形参)  
void Free\_Teacher01(Teacher \*\*p)  
\{  
Teacher \*tmp = NULL;  
if (p == NULL)  
\{  
printf("func err p == NULL\\n");  
\}  
tmp = \*p;//把二级指针还原成一级指针进行释放   
if (tmp != NULL)  
\{  
free(tmp);  
\}  
\*p = NULL;  
\}  
int  main()  
\{  
int ret = 0;  
int num = 3;  
//Teacher Array\[3\];//在栈上 分配内存  
//建立一个对象生命周期  
  
  
Teacher \*Array = NULL;  
//方法一 return方法  
  
  
Array = creatTeacher(num);  
if (Array == NULL)  
\{  
ret = -1;  
printf("func err creatTeacher:%d\\n", ret);  
return ret;  
\}  
//方法二 高一级指针（形参）来开辟空间(改变实参的值)  
  
  
//ret = creatTeacher01(&Array,num);  
//if (ret!=0)  
//\{  
// printf("func err creatTeacher01:%d",ret);  
// return ret;  
//\}  
for (int i = 0; i < num; i++)  
\{  
//scanf("%d%d%d",&a,&b,&c);  
printf("please input three integer number:\\n");  
scanf("%d", &(Array\[i\].age));  
\}  
  
  
//打印老师年龄  
  
  
printf("未排序之前\\n");  
printArray(Array, num);  
  
  
//排序 冒泡法  
sortArray(Array, num);  
//排序后 打印  
  
  
printf("未排序之后\\n");  
printArray(Array, num);  
  
  
//释放资源  
  
  
//1直接用形参释放 但是要另外加上一句置空  
Free\_Teacher(Array);  
Array = NULL;  
  
  
//2用高一级指针(形参),一句顶上面两句  
//Free\_Teacher01(&Array);  
printf("hello...");  
system("pause");  
return 0;  
\}