# include <stdio.h> struct student { /* 学生信息结构定义 */ int num; /* 学号 */ char name[10]; /* 姓名 */ int computer, english, math; /* 三门课程成绩 */ double average; /* 个人平均成绩 */ }; int main() { int i, n; struct student stu,max; /* 定义结构变量 */ printf ("Input n: "); scanf ("%d", &n); printf ("Input the student’s number, name and course scores\n"); for (i = 1; i <= n; i++){ printf ("No.%d: ", i); scanf ("%d%s%d%d%d",&stu.num,stu.name,&stu.math,&stu.english,&stu.computer); stu.average = (stu.math + stu.english + stu.computer) / 3.0; if (i == 1){ max = stu; /* 结构变量赋值 */ }else if (max.average < stu.average){ max = stu; } } printf("num:%d, name:%s, average:%.2lf\n", max.num, max.name, max.average); return 0; }向这个代码里面添加一个查询和修改学生的成绩功能

好的，可以尝试如下添加查询和修改学生成绩的代码：

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

struct student {                      /* 学生信息结构定义 */
    int num;                              /* 学号 */
    char name[10];                  /* 姓名 */
    int computer, english, math;      /* 三门课程成绩 */
    double average;                /* 个人平均成绩 */
};

int main() {
    int i, n, choice;
    struct student stu[100],max;                          /* 定义结构变量 */
    printf ("Input n: ");
    scanf ("%d", &n);
    printf ("Input the student’s number, name and course scores\n");
    for (i = 1; i <= n; i++){
        printf ("No.%d: ", i);
        scanf ("%d%s%d%d%d",&stu[i].num,stu[i].name,&stu[i].math,&stu[i].english,&stu[i].computer);
        stu[i].average = (stu[i].math + stu[i].english + stu[i].computer) / 3.0;
        if (i == 1){
            max = stu[i];                		/* 结构变量赋值 */
        }else if (max.average < stu[i].average){
            max = stu[i];
        }
    }
    printf("num:%d, name:%s, average:%.2lf\n", max.num, max.name, max.average);
    
    while(1) {
        printf("\nWhat do you want to do?\n");
        printf("1. Query student's grade\n");
        printf("2. Modify student's grade\n");
        printf("3. Exit\n");
        scanf("%d", &choice);
        switch(choice) {
            case 1:
                int num_query;
                printf("Input student's number to query: ");
                scanf("%d", &num_query);
                for(int j = 1; j <= n; j++) {
                    if(stu[j].num == num_query) {
                        printf("Student info: num:%d, name:%s, math:%d, english:%d, computer:%d, average:%.2lf\n", stu[j].num, stu[j].name, stu[j].math, stu[j].english, stu[j].computer, stu[j].average);
                        break;
                    }
                    if(j == n) {
                        printf("No student found with the number %d\n", num_query);
                    }
                }
                break;
            case 2:
                int num_modify, course_modify, new_grade;
                printf("Input student's number to modify: ");
                scanf("%d", &num_modify);
                printf("Which course grade do you want to modify? (1: math, 2: english, 3: computer) ");
                scanf("%d", &course_modify);
                printf("Input new grade: ");
                scanf("%d", &new_grade);
                for(int j = 1; j <= n; j++) {
                    if(stu[j].num == num_modify) {
                        switch(course_modify) {
                            case 1:
                                stu[j].math = new_grade;
                                break;
                            case 2:
                                stu[j].english = new_grade;
                                break;
                            case 3:
                                stu[j].computer = new_grade;
                                break;
                            default:
                                printf("Invalid input\n");
                                break;
                        }
                        stu[j].average = (stu[j].math + stu[j].english + stu[j].computer) / 3.0;
                        printf("Grade modified successfully!\n");
                        printf("New student info: num:%d, name:%s, math:%d, english:%d, computer:%d, average:%.2lf\n", stu[j].num, stu[j].name, stu[j].math, stu[j].english, stu[j].computer, stu[j].average);
                        break;
                    }
                    if(j == n) {
                        printf("No student found with the number %d\n", num_modify);
                    }
                }
                break;
            case 3:
                printf("Exit program.\n");
                return 0;
            default:
                printf("Invalid input\n");
                break;
        }
    }
    return 0;
}

这个程序添加了一个 while 循环，让用户可以重复进行查询和修改操作，直到选择退出程序。在查询学生成绩时，用户需要输入学生的学号，程序会遍历学生信息结构体数组，找到对应学号的学生信息并输出。在修改学生成绩时，用户需要输入学生的学号、想要修改的科目编号以及新的成绩，程序会根据这些信息修改对应学生的成绩，并重新计算平均成绩，最后输出修改后的学生信息。