c语言构造数据类型

1.

/*

typedef:给老的数据类型取别名;可以简写复杂的数据类型;

*/

typedef unsigned int ui;
typedef int *pint;//pint是个类型,int *的新名字;
typedef int (*pfunc)(int ,int );//pfunc是个类型,表示函数指针类型;

int add(int a,int b)
{
    return a+b;
}

int main(int argc, const char * argv[])
{
    ui a = 10;//用新的数据类型定义一个变量;
    printf("a=%u\n",a);

    int b=20;
    pint p = &b;//p是int *型
    printf("*p=%d\n",*p);
//    pint q[3];//指针数组;
    pfunc pf = add;//pf是个变量
    printf("add rst=%d\n",pf(a,b));
    return 0;
}

2.

/*

结构体:关键字 struct

*/

#include <string.h>
struct student//定义了一种新的数据类型;
{
    char name[20];//成员变量;存储空间说明:加入是一个鞋柜,char占20个字节,需要20个空间,int 需要4的字节空间,所以工需要28个空间;
    int age;
    int height;
};
typedef struct student stu;

typedef struct student//定义了一种新的数据类型;
{
    char name[20];//成员变量;
    int age;
    int height;
}stu;

int main()
{
    struct student xiaoming = {"xiaoming",18,188};//struct student是数据类型:xiaoming是变量名;
    printf("sizeof(struct student) is %lu\n",sizeof(struct student));
    //访问结构体的成员变量
    xiaoming.age=30;
    //1:改名字
    strcpy(xiaoming.name,"wangcai");
    //2:升级
    strcat(xiaoming.name,"6s");

    printf("name:%s,age:%d,height:%d\n",xiaoming.name,xiaoming.age,xiaoming.height);

    stu xiaohong = {"xiaohong",18,165};
    printf("name:%s,age:%d,height:%d\n",xiaohong.name,xiaohong.age,xiaohong.height);
    return 0;
}

#include <stdlib.h>

typedef struct student//定义了一种新的数据类型;
{
    char name[20];//成员变量;
    int age;
    int height;
}stu;

int main()
{
    stu class[10]={};
    stu *pst;//pst就是一个指针,stu是pst指向的数据类型;pst可以指向class里的任何一个元素;
    //给数组所在元素赋值
    class[0].age = 18;
    //name :ios1518+2位学号
    //height :180,175~180之间浮动
    //age :15~24
    for(int i=0;i<10;i++)
    {
        sprintf(class[i].name,"ios1518%02d",i+1);
        class[i].age = 15+i;
        class[i].height=random()%10+175;//random()表示是随机数;random()%10表示取0~9之间的任意数字;
    }
    //遍历学生信息
    for(int i=0;i<10;i++)
    {
        printf("name=%s,age=%d,height=%d\n",class[i].name,class[i].age,class[i].height);
    }
    //按照身高排序:排序的主体是数组的元素,但key是元素的身高,排序需要将整个构造体全部元素进行排序
    for(int i=0;i<10-1;i++)
    {
        for(int j=0;j<10-i-1;j++)
        {
            if(class[j].height>class[j+1].height)
            {
                stu temp = class[j];
                class[j] = class[j+1];
                class[j+1] = temp;
            }
        }
    }
    printf("========================================\n");
    //遍历学生信息
    for(int i=0;i<10;i++)
    {
        printf("name=%s,age=%d,height=%d\n",class[i].name,class[i].age,class[i].height);
    }

    //使用pst指针访问数组,
//    pst = &class[0];//指针指向首个元素
    pst = class;
    printf("sizeof(stu)=%lu,sizeof(class)=%lu\n",sizeof(stu),sizeof(class));
    //访问第一个元素
    printf("first info ,name:%s,age:%d,height:%d\n",pst->name,pst->age,pst->height);
    printf("=========================================\n");
     //遍历学生信息
    for(int i=0;i<10;i++)
    {
        printf("name:%s,age:%d,height:%d\n",(pst+i)->name,(pst+i)->age,(pst+i)->height);
    }
}

typedef struct student
{
    char name[20];
    int age;
    int height;
    union//联合体:二选一的关系
    {
        int stuid;
        char nickname[20];
    };
    /*
     共享同一段内存,按情况去解析;
     内存大小按大的计算;//所以此结构体占用的内存是20+4+4+20=48字节;
     初始化的时候,按照第一个解析;
     */
}stu1;

int main()
{
    stu1 xiaohong = {"xiaohong",20,165,0};//开始的时候只能按照int进行初始化,不能用nickname;
    strcpy(xiaohong.nickname, "旺财");
    printf("%s\n",xiaohong.nickname);
    return 0;
}

3.

/*

枚举:一枚一枚的举出来;把一个变量的合理取值列举出来;

枚举是整形常量,把变量的合理取值列举出来;

列举的常量,默认从0开始,后面一次加1;

*/

typedef enum weekday
{
    Monday=1,//可设置,后面按照设置的值一次加1;
    Tuesday,
    Wednesday,
    Thursday,
    Firday,
    Saturday,
    Sunday
}WEEKDAY;
int main()
{
//    enum weekday day;
    WEEKDAY day;
    printf("sizeof(day)=%lu\n",sizeof(day));//sizeof(day)=4,因为其实际保存的都是int类型;
    printf("Monday=%d\n",Monday);
    printf("Sunday=%d\n",Sunday);
    printf("请输入周几\n");
    scanf("%d",&day);
    switch (day)
    {
        case Monday:
            printf("Monday\n");
            break;
        case Tuesday:
            printf("Tuesday\n");
            break;
        case Wednesday:
            printf("Wednesday\n");
            break;
        case Thursday:
            printf("Thursday\n");
            break;
        case Firday:
            printf("Firday\n");
            break;
        case Saturday:
            printf("Saturday\n");
            break;
        case Sunday:
            printf("Sunday\n");
            break;
        default:
            printf("error\n");
            break;
    }
    return 0;

}

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