使用整型数组保存30名学生的学号，6门课程的编号，以及对应的成绩，使 用字符数组保存这30名学生学号和姓名，使用字符数组保存这6门课程编号对应 的课程名称，能通过学号和课程号将三个数组进行关联。能够按学号或姓名查询 所有课程的成绩，能添加/删除/更新学生各门课程的成绩记录:能够修改指定姓 名或学号的学生的课程成绩;显示指定课程编号输出60分以下、60-79、80-89 90分以上各分数段的学生信息。。 要求: ①提供系统操作的主界面: 2通过学号查询该学生所有课程的总分和平均分 通过课程编号查询该门课程的平均分，大于平均分的学生姓名 ④自行设计相关功能: 写对不同的功能设计不同的函数，完成函数的级计和调用。

实现这个系统，需要设计以下几个函数：

1. `void init()`：初始化学生学号、课程编号和成绩数组，以及学生姓名和课程名称数组。

2. `void addStudent()`：添加学生信息，包括学号和姓名。

3. `void deleteStudent()`：删除指定学生信息，包括学号、姓名和成绩记录。

4. `void updateScore()`：更新指定学生指定课程的成绩记录。

5. `void queryScoreByStudent()`：按学生学号或姓名查询所有课程的成绩。

6. `void queryScoreByCourse()`：按课程编号查询该门课程的平均分和大于平均分的学生姓名。

7. `void queryScoreByGrade()`：按课程编号查询该门课程的成绩分数段和对应学生信息。

下面是一个可能的实现：

#include <iostream>
#include <cstring>

using namespace std;

const int MAX_STUDENT_NUM = 30;
const int MAX_COURSE_NUM = 6;
const int SCORE_BOUNDARIES[3] = {60, 80, 90};

int studentIds[MAX_STUDENT_NUM];
int courseIds[MAX_COURSE_NUM];
int scores[MAX_STUDENT_NUM][MAX_COURSE_NUM];
char studentNames[MAX_STUDENT_NUM][20];
char courseNames[MAX_COURSE_NUM][20];

int studentNum = 0;
int courseNum = 0;

void init() {
    // 初始化学生学号、课程编号和成绩数组
    for (int i = 0; i < MAX_STUDENT_NUM; i++) {
        studentIds[i] = -1;
        for (int j = 0; j < MAX_COURSE_NUM; j++) {
            scores[i][j] = -1;
        }
    }
    for (int i = 0; i < MAX_COURSE_NUM; i++) {
        courseIds[i] = -1;
    }

    // 初始化学生姓名和课程名称数组
    strcpy(studentNames[0], "张三");
    strcpy(studentNames[1], "李四");
    strcpy(studentNames[2], "王五");

    strcpy(courseNames[0], "数学");
    strcpy(courseNames[1], "语文");
    strcpy(courseNames[2], "英语");

    // 初始化学生学号和课程编号
    studentIds[0] = 1001;
    studentIds[1] = 1002;
    studentIds[2] = 1003;

    courseIds[0] = 2001;
    courseIds[1] = 2002;
    courseIds[2] = 2003;

    studentNum = 3;
    courseNum = 3;
}

int findStudentIndexById(int id) {
    for (int i = 0; i < studentNum; i++) {
        if (studentIds[i] == id) {
            return i;
        }
    }
    return -1;
}

int findStudentIndexByName(const char* name) {
    for (int i = 0; i < studentNum; i++) {
        if (strcmp(studentNames[i], name) == 0) {
            return i;
        }
    }
    return -1;
}

int findCourseIndexById(int id) {
    for (int i = 0; i < courseNum; i++) {
        if (courseIds[i] == id) {
            return i;
        }
    }
    return -1;
}

void addStudent() {
    if (studentNum == MAX_STUDENT_NUM) {
        cout << "学生人数已达上限，无法添加。" << endl;
        return;
    }

    int id;
    char name[20];

    cout << "请输入学号：";
    cin >> id;

    // 检查学号是否已存在
    if (findStudentIndexById(id) != -1) {
        cout << "该学号已存在，请重新输入。" << endl;
        return;
    }

    cout << "请输入姓名：";
    cin >> name;

    // 添加学号和姓名
    studentIds[studentNum] = id;
    strcpy(studentNames[studentNum], name);

    studentNum++;

    cout << "添加成功。" << endl;
}

void deleteStudent() {
    int id;
    char name[20];

    cout << "请输入要删除的学生的学号或姓名：";
    cin >> name;

    // 先按学号查找，再按姓名查找
    int index = findStudentIndexById(atoi(name));
    if (index == -1) {
        index = findStudentIndexByName(name);
    }

    if (index == -1) {
        cout << "未找到该学生。" << endl;
        return;
    }

    // 删除学生信息
    studentIds[index] = -1;
    strcpy(studentNames[index], "");

    // 删除成绩记录
    for (int i = 0; i < courseNum; i++) {
        scores[index][i] = -1;
    }

    cout << "删除成功。" << endl;
}

void updateScore() {
    int id;
    char name[20];
    int courseId;
    int score;

    cout << "请输入要修改成绩的学生的学号或姓名：";
    cin >> name;

    // 先按学号查找，再按姓名查找
    int index = findStudentIndexById(atoi(name));
    if (index == -1) {
        index = findStudentIndexByName(name);
    }

    if (index == -1) {
        cout << "未找到该学生。" << endl;
        return;
    }

    cout << "请输入要修改成绩的课程编号：";
    cin >> courseId;

    // 查找课程编号的索引
    int courseIndex = findCourseIndexById(courseId);
    if (courseIndex == -1) {
        cout << "未找到该课程。" << endl;
        return;
    }

    cout << "请输入新的成绩：";
    cin >> score;

    scores[index][courseIndex] = score;

    cout << "修改成功。" << endl;
}

void queryScoreByStudent() {
    int id;
    char name[20];

    cout << "请输入要查询成绩的学生的学号或姓名：";
    cin >> name;

    // 先按学号查找，再按姓名查找
    int index = findStudentIndexById(atoi(name));
    if (index == -1) {
        index = findStudentIndexByName(name);
    }

    if (index == -1) {
        cout << "未找到该学生。" << endl;
        return;
    }

    cout << "学号：" << studentIds[index] << "，姓名：" << studentNames[index] << endl;

    for (int i = 0; i < courseNum; i++) {
        cout << courseNames[i] << "：" << scores[index][i] << endl;
    }
}

void queryScoreByCourse() {
    int courseId;

    cout << "请输入要查询成绩的课程编号：";
    cin >> courseId;

    // 查找课程编号的索引
    int courseIndex = findCourseIndexById(courseId);
    if (courseIndex == -1) {
        cout << "未找到该课程。" << endl;
        return;
    }

    int sum = 0;
    int count = 0;

    // 计算平均分
    for (int i = 0; i < studentNum; i++) {
        if (scores[i][courseIndex] != -1) {
            sum += scores[i][courseIndex];
            count++;
        }
    }

    if (count == 0) {
        cout << "该课程还没有成绩记录。" << endl;
        return;
    }

    double average = (double)sum / count;

    cout << "平均分：" << average << endl;

    cout << "成绩大于平均分的学生姓名：" << endl;
    for (int i = 0; i < studentNum; i++) {
        if (scores[i][courseIndex] > average) {
            cout << studentNames[i] << endl;
        }
    }
}

void queryScoreByGrade() {
    int courseId;

    cout << "请输入要查询成绩的课程编号：";
    cin >> courseId;

    // 查找课程编号的索引
    int courseIndex = findCourseIndexById(courseId);
    if (courseIndex == -1) {
        cout << "未找到该课程。" << endl;
        return;
    }

    int count[3] = {0, 0, 0};

    cout << "60分以下：" << endl;
    for (int i = 0; i < studentNum; i++) {
        if (scores[i][courseIndex] < SCORE_BOUNDARIES[0]) {
            cout << "学号：" << studentIds[i] << "，姓名：" << studentNames[i] << "，成绩：" << scores[i][courseIndex] << endl;
            count[0]++;
        }
    }

    cout << "60-79分：" << endl;
    for (int i = 0; i < studentNum; i++) {
        if (scores[i][courseIndex] >= SCORE_BOUNDARIES[0] && scores[i][courseIndex] < SCORE_BOUNDARIES[1]) {
            cout << "学号：" << studentIds[i] << "，姓名：" << studentNames[i] << "，成绩：" << scores[i][courseIndex] << endl;
            count[1]++;
        }
    }

    cout << "80-89分：" << endl;
    for (int i = 0; i < studentNum; i++) {
        if (scores[i][courseIndex] >= SCORE_BOUNDARIES[1] && scores[i][courseIndex] < SCORE_BOUNDARIES[2]) {
            cout << "学号：" << studentIds[i] << "，姓名：" << studentNames[i] << "，成绩：" << scores[i][courseIndex] << endl;
            count[2]++;
        }
    }

    cout << "90分以上：" << endl;
    for (int i = 0; i < studentNum; i++) {
        if (scores[i][courseIndex] >= SCORE_BOUNDARIES[2]) {
            cout << "学号：" << studentIds[i] << "，姓名：" << studentNames[i] << "，成绩：" << scores[i][courseIndex] << endl;
        }
    }

    cout << "成绩分布：" << endl;
    cout << "60分以下：" << count[0] << "人，" << (double)count[0] / studentNum * 100 << "%" << endl;
    cout << "60-79分：" << count[1] << "人，" << (double)count[1] / studentNum * 100 << "%" << endl;
    cout << "80-89分：" << count[2] << "人，" << (double)count[2] / studentNum * 100 << "%" << endl;
    cout << "90分以上：" << studentNum - count[0] - count[1] - count[2] << "人，" << (double)(studentNum - count[0] - count[1] - count[2]) / studentNum * 100 << "%" << endl;
}

int main() {
    init();

    int choice;

    do {
        cout << "请选择操作：" << endl;
        cout << "1. 添加学生信息" << endl;
        cout << "2. 删除学生信息" << endl;
        cout << "3. 更新学生成绩" << endl;
        cout << "4. 按学号或姓名查询学生成绩" << endl;
        cout << "5. 按课程编号查询课程成绩" << endl;
        cout << "6. 按课程编号查询成绩分布" << endl;
        cout << "0. 退出" << endl;
        cin >> choice;

        switch (choice) {
            case 1:
                addStudent();
                break;
            case 2:
                deleteStudent();
                break;
            case 3:
                updateScore();
                break;
            case 4:
                queryScoreByStudent();
                break;
            case 5:
                queryScoreByCourse();
                break;
            case 6:
                queryScoreByGrade();
                break;
            case 0:
                break;
            default:
                cout << "无效的操作，请重新选择。" << endl;
                break;
        }
    } while (choice != 0);

    return 0;
}