C语言基础_高级指针

一、结构体指针

1）结构体指针 指针指向结构体的存储单元 先对结构体的变量取地址

2）p指向结构体的起始地址 就是首个成员变量的地址

typedef struct teacher{
    char name[20];
    int age;
}Teacher;
int main(int argc, const char * argv[]) {
    Teacher t1 = {"laoluo",20};
    Teacher *p = &t1;
    printf("p = %p,name = %p,age = %p\n",p,t1.name,&t1.age);
return 0;
}

3) 通过结构体指针访问成员变量

（*P).name    (*p):p指向结构体的存储单元

typedef struct teacher{
    char name[20];
    int age;
}Teacher;
int main(int argc, const char * argv[]) {

    Teacher t2 = {"hahazheng",23};
    Teacher *p1 = &t2;
    strcpy((*p1).name, "memeda");
    (*p1).age = 24;
    printf("%s %d\n",(*p1).name,(*p1).age);
    return 0;
}

4) 通过箭头访问 p -> name;

typedef struct teacher{
    char name[20];
    int age;
}Teacher;
int main(int argc, const char * argv[]) {

    Teacher t3 = {"heheda",22};
    Teacher *p1 = &t3;
    p1 -> age = 20;
    printf("%s %d\n",p1->name,p1->age);

    return 0;
}

5) 求坐标两点之间的距离

typedef struct cpoint{
    float x;
    float y;
}CPoint;
float TwoPoint(CPoint *ps,CPoint *pd){
    float dx = ps->x - pd->x;
    float dy = ps->y - pd->y;
    float dz = sqrtf(dx*dx + dy*dy);
    return dz;

}
int main(int argc, const char * argv[]) {

    CPoint m ={0.0,4.0};
    CPoint n = {3.0,0.0};
    CPoint *ps = &m;
    CPoint *pd = &n;

    printf("两点之间的距离为:%f",TwoPoint(ps, pd));
    return 0;
}

6）字符串操作

typedef struct student{
    int number;
    char name[20];
    char gender;
    float score;
}Student;

int main(int argc, const char * argv[]) {

    Student stu = {1,"lan ou",‘m‘,95.6};
    Student *pl = &stu                ;
    int length = (int)strlen(pl->name);
    for (int i =0; i < length ; i++) {
        if (i == 0 && (*(pl->name) >=‘a‘ && *(pl->name)<=‘z‘)){
 //pl->name拿到name字符串 因为自己字符串本身是有地址的  [Student *pl = &stu][拿到首地址] 所以(*(pl->name)）就是拿到字符串的首地址(首字母)
            *(pl->name) = *(pl->name) - 32;
        }
        if (*((pl->name)+i) == ‘ ‘) {
            *((pl->name)+i) =‘_‘;
        }
    }
    printf("%s\n",pl->name);
    return 0;

}

二、结构体数组

typedef struct student{
    char name[20];
    int age;
    char gender;
    float score;

}Student;
int main(int argc, const char * argv[]) {

Student stu3[3] = {{"liubei",100,‘m‘,23},{"guanyu",17,‘m‘,90},{"zhangfei",18,‘m‘,78}};
    Student *ss = stu3;
    printf("%s\n",stu3[0].name);
    printf("%s\n",ss[0].name);
    printf("%s\n",ss->name);
    printf("%f\n",(*(ss+1)).score);
    printf("%d\n",(*(ss+2)).age);
    printf("%f\n",(ss+2)->score);
    printf("%d\n",(int)sizeof(Student));
    for (int i =0; i<3; i++) {
        printf("%s %d %c %.2f\n",(ss+i)->name,(ss+i)->age,(ss+i)->gender,(ss+i)->score);
    }
    return 0;
}

三、结构件指针作为函数参数

typedef struct person{
    char name[20];
    int age;
    char gender;
    float weight;
}Person;
typedef struct student{
    char name[20];
    int age;
    char gender;
    float score;

}Student;
void maxWeight(Person *p3,Person *p4){
    Person *max = p3->weight > p4->weight ? p3:p4;//p3 p4指向结构体的起始地址 就是首个成员变量的地址 所以再将它赋值给新的指针变量时 并不需要重新获得地址
    printf("%s %d %c %.2f\n",max->name,max->age,max->gender,max->weight);
}
int main(int argc, const char * argv[]) {

    Person p1 = {"gailun",18,‘m‘,110};
    Person p2 = {"liqing",30,‘m‘,125};

    Person *p3 = &p1;
    Person *p4 = &p2;
    maxWeight(p3, p4);

    Student stu1 = {"chengmanxiang",27,‘f‘,99};
    Student *s = &stu1;
    (*s).age = 18;
    s->gender = ‘m‘;
    printf("%c\n",(*s).gender);
    printf("%s\n",s->name);

    return 0;
}

四、结构体数组作为函数参数

typedef struct student{
    char name[20];
    int age;
    char gender;
    float score;

}Student;
void printStudent(Student *stu,int n){
    for (int i =0; i<n; i++) {
        if(((stu+i)->gender) != ‘f‘){
            ((stu+i)->gender) = ‘f‘;
        }
    printf("%s %d %c %f\n",(stu+i)->name,stu[i].age,(*(stu+i)).gender,(stu+i)->score);
    }
    printf("/////////////////////////////////////\n");
    //按年龄排序
    for (int i = 0; i < n-1; i++) {
        for (int j =0; j< n-1-i; j++) {
            if ((stu+j)->age > (stu+j+1)->age) {
                Student temp = stu[j];
                stu[j] = stu[j+1];
                stu[j+1] = temp;
            }
        }
    }
    for (int i =0; i<n; i++) {
    printf("%s %d %c %f\n",(stu+i)->name,stu[i].age,(*(stu+i)).gender,(stu+i)->score);
    }
    printf("/////////////////////////////////////\n");
}

int main(int argc, const char * argv[]) {

    Student stu4[4] = {{"kate",18,‘f‘,65},{"yasuo",30,‘m‘,400},{"zelasi",29,‘?‘,30},{"guafu",23,‘f‘,89}};
    Student *stu = stu;//为什么没有取地址符&  因为数组本身是有地址的 stu指向首个成员变量的地址
    printStudent(stu4, 4);

    return 0;
}