指针函数int max(int a, int b);

     *   函数指针:指向一个函数的指针变量.‘

     *   函数的类型:返回值类型+参数

     *   函数指针变量类型: int (*)(int x, int y)

     *   指针变量的名字:max

     *   初始值:NULL

     *   max 可以指向一个返回值是int型并且有两个int型的参数的函数.

应用:学生结构体按照姓名,年龄,分数升序排序

1.函数的声明

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

typedef BOOL (*ALL)(Student, Student);

typedef struct nameFunctionPair{
    char name[10];//名字
    ALL p; //对应的函数地址
}NameFunctionPair;


//年龄
BOOL compareByAge(Student stu1 , Student stu2);

//成绩
BOOL compareByScore(Student stu1 , Student stu2);

//姓名
BOOL compareByName(Student stu1 , Student stu2);

//排序
void sortStudent(Student *p, int cont , ALL a);

//输出所有学生的信息
void outputStudent(Student *p, int count);

//从匹配表中匹配到对应的函数地址.
ALL matchFunctionByName(NameFunctionPair *q, int count ,char *name);//*p接收匹配表数组.count.接受匹配表数组的元素个数.name.接受用户输入的内容.<span style="color:#ff0000;">

</span>

//输出所有学生的信息
void outputStudent(Student *p ,int count) {
    for (int i = 0; i < count; i++) {
        printf("%s,%d,%.1f\n",p[i].name,p[i].age,p[i].score );
    }
}

//年龄
BOOL compareByAge(Student stu1 , Student stu2){
    return stu1.age > stu2.age;
}

//成绩
BOOL compareByScore(Student stu1 , Student stu2) {
    return stu1.score > stu2.score;
}

//姓名

BOOL compareByName(Student stu1 , Student stu2) {
    return strcmp(stu1.name, stu2.name) > 0;
}

//排序
void sortStudent(Student *p, int count ,ALL a) {
    
    for (int i = 0; i < count - 1; i++) {
        for (int j = 0; j < count - 1 - i; j++) {
            if (a(p[j], p[j + 1])) {
                Student temp = p[j];
                p[j] = p[j + 1];
                p[j + 1] = temp;
            }
        }
    }
    
}
ALL matchFunctionByName(NameFunctionPair *q, int count ,char *name) {
    
    for (int i = 0; i < count ; i++) {
        if (strcmp(q[i].name, name) == 0) {
            return q[i].p;
        }
    }
    return NULL;//如果没有匹配成功返回NULL.
}

 

    Student stu[5] = {
        {"zhangs", 24, 78.9},
        {"xiaom", 18, 45.8},
        {"xiaozhen", 19,56.0},
        {"heh", 20, 64.8},
        {"frak", 19, 79.0}
    };
    
    NameFunctionPair name[3] = {
        {"age", compareByAge},
        {"score", compareByScore},
        {"name", compareByName}
    };
    
    while (YES) {
    char temp[10] = {0};
    printf("name-姓名,age-年龄,socre-分数:\n");
    scanf("%s",temp);
    //根据用户输入内容匹配到对应的函数
    ALL al = matchFunctionByName(name, 3, temp);
    if (al != NULL) {//while(p == NULL)
        //根据匹配到的内容进行排序.
        sortStudent(stu, 5, al);
        outputStudent(stu, 5);
    } else if (al == NULL) {
        printf("你输入的字符串不正确!请重新输入\n");
        
    }
}

1.随机生成一个10个元素的数组,找到3的倍数,并将其值修改成0.(注意:修改数值使用回掉函数处理)

1.函数声明

typedef int (*ZERO)(int,int);

//随机10个元素的数组
void getTenNumber(int *p, const int count);
//遍历去除元素
void outputNumber(int *p, const int count);

//找到3的倍数,并且赋值为0
void findNumberToZero(int *p, const int count, ZERO z, int n);

//找n的倍数,
int copyZero(int number,int n);

//随机10个元素的数组
void getTenNumber(int *p, const int count) {
    for (int i = 0; i < count; i++) {
        p[i] = arc4random() % (40 - 10 + 1) + 10;
    }
}

//遍历取出元素的个数
void outputNumber(int *p, const int count) {
    for (int i = 0; i < count; i++) {
        printf("%d ",p[i]);
    }
}


//找到3的倍数,并且赋值为0
void findNumberToZero(int *p, const int count ,ZERO z,int n) {
    for (int i = 0; i < count; i++) {
        if (z(p[i],n) == 0) {
            p[i] = 0;
        }
    }
}

int copyZero(int number ,int n) {
    if (n == 0) {
        return NO;
    }
    return number % n;
}

   

 int arr[10] = {0};
    getTenNumber(arr, 10);
    outputNumber(arr, 10);
    //4对应找到3的倍数,
    findNumberToZero(arr, 10, copyZero, 4);
    printf("\n");
    outputNumber(arr, 10);

【学习ios之路:C语言】指针函数