定义定一个结构体类型student，写一个函数，根据学号或者成绩，对包含有n个学生的结构体数组进行排序，学生的结构体至少包括3个成员（学号，姓名，入学分数等），比较结构体变量的大小时，可以根据其学号或者分

数进行比较。

具体实现如下：

#include <stdio.h>
#include <string.h>

#define MAX_NUM 100

typedef struct {
    int id;
    char name[20];
    int score;
} Student;

void print_student(Student stu) {
    printf("%d\t%s\t%d\n", stu.id, stu.name, stu.score);
}

void print_students(Student *students, int n) {
    printf("ID\tName\tScore\n");
    for (int i = 0; i < n; i++) {
        print_student(students[i]);
    }
}

int cmp_by_id(const void *a, const void *b) {
    Student *s1 = (Student *)a;
    Student *s2 = (Student *)b;
    return s1->id - s2->id;
}

int cmp_by_score(const void *a, const void *b) {
    Student *s1 = (Student *)a;
    Student *s2 = (Student *)b;
    return s1->score - s2->score;
}

void sort_students(Student *students, int n, int (*cmp)(const void *, const void *)) {
    qsort(students, n, sizeof(Student), cmp);
}

int main() {
    Student students[MAX_NUM] = {
        {101, "Alice", 80},
        {102, "Bob", 90},
        {103, "Charlie", 70},
        {104, "David", 85},
        {105, "Eve", 95},
    };
    int n = 5;

    printf("Before sorting:\n");
    print_students(students, n);

    sort_students(students, n, cmp_by_id);
    printf("After sorting by ID:\n");
    print_students(students, n);

    sort_students(students, n, cmp_by_score);
    printf("After sorting by score:\n");
    print_students(students, n);

    return 0;
}

运行结果如下：

Before sorting:
ID      Name    Score
101     Alice   80
102     Bob     90
103     Charlie 70
104     David   85
105     Eve     95
After sorting by ID:
ID      Name    Score
101     Alice   80
102     Bob     90
103     Charlie 70
104     David   85
105     Eve     95
After sorting by score:
ID      Name    Score
103     Charlie 70
101     Alice   80
104     David   85
102     Bob     90
105     Eve     95