结构体进阶

c

结构体的基础操作

#include <stdio.h>
#include <stdlib.h>
#include <string.h>
//1.自己定义一个数据类型,数据类型的本质是固定大小内存块的别名
//2..c和.cpp定义结构体类型定义变量的时候，c和c++编译器的处理行为不一样
//3.结构体类型typedef
//4.结构变量内存四字节存放，
typedef struct Teacher 
{
    char name[62];
    int age;
    char title[128];
    /************************************************************************/
    /*
    char name[62]; // 62字节
    char c1;        //1字节
    char c2;        //1字节
    int age;        //4字节
    一共68字节                                                              */
    /************************************************************************/
    /************************************************************************/
    /*
    char name[62];  //62字节
    char c1;        //63 + 1空闲字节
    int age;        //4字节
    char c2;        //1字节 + 3空闲字节
    一共72字节                                                              */
    /************************************************************************/
}Teacher;
//结构体变量的初始化3种方法
//结构体定义变量的4种方法
//结构体变量的复制方法，操作结构体变量
void main()
{
    //告诉编译器要分配内存
    struct Teacher  t1; /*使用struct Teacher直接定义*/
    Teacher t2 = { "dddd", 40, "dffd" };/*只有使用了tyededef重命名了结构体才能这样用*/
    /*常用的初始化方法就上面一种*/
    printf("sizeof(char):%d\n", sizeof(char));
    t1.age = 10; /*通过.直接赋值*/
    Teacher *p = NULL; /*通过指针间接赋值*/
    p = &t1;
    p->age = 20;
    printf("sizeof(Teacher):%d\n", sizeof(t1));
    system("pause");
}

结构体进阶

#include <stdio.h>
#include <stdlib.h>
#include <string.h>
typedef struct Teacher
{
    char name[62];
    int age;
}Teacher;
void printfArray(Teacher *p, int count)
{
    for (int i = 0; i < count; ++i)
    {
        printf("%d\n", p[i].age);
    }
}
Teacher *createTarray(int count)
{
    Teacher *p = (struct Teacher *)malloc(count * sizeof(Teacher));
    if (p == NULL)
    {
        return;
    }
    for (int i = 0; i < count; ++i)
    {
        memset(&p[i], 0, sizeof(Teacher));
        //或者 memset(p1 + i, 0, sizeof(Teacher)); 
    }
    return p;
}
int sortArray(Teacher *p, int num)
{
    Teacher tmp;
    for (int i = 0; i < num; ++i)   
    {
        for (int j = i + 1; j < num; ++j)
        {
            if (p[i].age < p[j].age)
            {
                memcpy(&tmp, &p[i], sizeof(Teacher));
                memcpy(&p[i], &p[j], sizeof(Teacher));
                memcpy(&p[j], &tmp, sizeof(Teacher));
            }
        }
    }
    return 0;
}
void freeMem(Teacher *p, int count)
{
    if (p != NULL)
    {
        free(p);
        p = NULL; //垃圾，写了和没写一个样
    }
//  for (int i = 0; i < count; ++i)
//  {
//      if (p[i] != NULL)
//      {
//          free(p[i]);
//      }
//  }
}
void main()
{
    Teacher tArray[10];
    Teacher *pArray = createTarray(4); //在堆上分配内存
    for (int i = 0; i < 4; ++i)
    {
        printf("请输入age:");
        scanf_s("%d", &tArray[i].age); //要改变实参的值
    }
    printfArray(tArray, 4);
    sortArray(tArray, 4);
    printfArray(tArray, 4);
    system("pause");
}

包含指针的结构体

#include <stdio.h>
#include <stdlib.h>
#include <string.h>
typedef struct Teacher
{
    char name[62];
    char *a_name;
    int age;
}Teacher;
void printfArray(Teacher *p, int count)
{
    for (int i = 0; i < count; ++i)
    {
        printf("%s %d\n", p[i].a_name, p[i].age);
    }
}
Teacher *createTarray(int count)
{
    Teacher *p = (struct Teacher *)malloc(count * sizeof(Teacher));
    if (p == NULL)
    {
        return NULL;
    }
    for (int i = 0; i < count; ++i)
    {
        memset(&p[i], 0, sizeof(Teacher));
        p[i].a_name = (char *)malloc(128 * sizeof(char));
        memset(p[i].a_name, 0, 128 * sizeof(char));
        //或者 memset(p1 + i, 0, sizeof(Teacher)); 
    }
    return p;
}
int sortArray(Teacher *p, int num)
{ //按照年龄排序
    Teacher tmp;
    for (int i = 0; i < num; ++i)
    {
        for (int j = i + 1; j < num; ++j)
        {
            if (p[i].age < p[j].age)
            {
                memcpy(&tmp, &p[i], sizeof(Teacher));
                memcpy(&p[i], &p[j], sizeof(Teacher));
                memcpy(&p[j], &tmp, sizeof(Teacher));
            }
        }
    }
    return 0;
}
void freeMem(Teacher *p, int count)
{
    if (p == NULL)
    {
        return;
    }
    for (int i = 0; i < count; ++i)
    {
        if (p[i].a_name != NULL)
        {
            free(p[i].a_name);
        }
    }
    if (p != NULL) //这里特别小心,怎样分配，怎样释放
    {
        free(p);
        p = NULL; //垃圾代码，写了和没写一个样
    }
}
void main()
{
    Teacher tArray[10];
    Teacher *pArray = createTarray(4); //在堆上分配内存
    for (int i = 0; i < 4; ++i)
    {
        printf("请输入别名:");
        scanf_s("%s", pArray[i].a_name); //要改变实参的值
        printf("请输入age:");
        scanf_s("%d", &tArray[i].age); //要改变实参的值
    }
    printfArray(tArray, 4);
    sortArray(tArray, 4);
    printfArray(tArray, 4);
    freeMem(pArray, 4); //释放堆上的数据
    system("pause");
}