C语言基础_函数指针

int maxValue(int a,int b){
    return  a > b ? a : b;
}
int （*p）(int,int) = maxvalwe;
    printf("%d\n",p(3,4));  //用指针去调用函数

int maxValue(int a,int b){
    return  a > b ? a : b;
}
int sumValue(int a,int b){   
    int sum = a+b;
    return sum;  
}
int main(int argc, const char * argv[]) {
    int (*p)(int,int) = NULL;
    int n = 0;
    scanf("%d",&n);
    switch (n) {
        case 1:
            p = maxValue;
            break;
        case 2:
            p = sumValue;
            break;
        default:
            printf("不在服务区");
            break;
    }
    if (p!=NULL) {
        printf("%d",p(3,5));
    }
  return 0;  
}

typedef struct student{
    char name[20];
    char gender;
    int age;
    float score;
}Student;
void print(char *name){
    strcat(name, "高富帅");
}
void findvalue(Student *s,int count,void(*p)(char *)){
    for (int i =0; i<count; i++) {
        if (s[i].score > 90) {
            p(s[i].name);
        }
        printf("%s %c %d %f\n",s[i].name,s[i].gender,s[i].age,s[i].score);
    }
}
int main(int argc, const char * argv[]) {
    Student stu[3] = {{"xiao",‘m‘,23,70},{"ming",‘f‘,24,91},{"zhang",‘m‘,28,95}};
    Student *s = stu;
    findvalue(s,3,print);
   return 0;  
}

typedef struct student{
    char name[20];
    char gender;
    int age;
    float score;
}Student;
typedef BOOL(*sortAll)(Student stu1,Student stu2);//定义一个函数指针类型
void sortStudent(Student *s,int count,sortAll al)//函数指针指向函数(sortAge)
{
    for (int i = 0; i < count-1; i++) {
        for (int j = 0; j < count-1-i; j++) {
            //函数回调
            if (al(s[j],s[j+1])) {
                Student temp = s[j];
                s[j]  = s[j+1];
                s[j+1] = temp;
            }
            /*通过函数指针al指向函数(sortAge)
             *所以s[j],s[j+1]这两个参数也指向函数(sortAge)的形参变量stu1,stu2
              if(al(s[j]),s[j+1]) 等价于 if(s[j].age > s[j+1].age)
             */
        }
    }
    for (int i =0; i<count; i++) {
        printf("%s %c %d %.2f\n",s[i].name,s[i].gender,s[i].age,s[i].score);
    }
}
BOOL sortAge(Student stu1,Student stu2)
{
    return stu1.age > stu2.age;
}
int main(int argc, const char * argv[]) {
    Student stu[3] = {{"xiao",‘m‘,23,70},{"ming",‘f‘,24,91},{"zhang",‘m‘,28,95}};
    Student *s = stu;
    sortStudent(s,3,sortAge);
    return 0;  
}