定义学生类，包括学号、姓名、性别、多门课程的成绩；假设有n个学生，由键盘输入 学生信息； 定义类成员函数，计算每个学生的平均成绩； 按课程统计每门课程的平均成绩、最高分和最低分； 同时输出所有学生信息； 通过输入学生学号或姓名查询某学生的信息。

class Student {
private:
int stu_id; //学号
string name; //姓名
char gender; //性别
vector<double> grades; //多门课程的成绩

public:
Student(int id, string n, char g, vector<double> gds) {
stu_id = id;
name = n;
gender = g;
grades = gds;
}

double getAverage() {
double sum = 0;
for (int i = 0; i < grades.size(); i++) {
sum += grades[i];
}
return sum / grades.size();
}

int getId() {
return stu_id;
}

string getName() {
return name;
}

char getGender() {
return gender;
}

vector<double> getGrades() {
return grades;
}
};

class School {
private:
vector<Student> students;

public:
void addStudent(Student s) {
students.push_back(s);
}

void printAllStudents() {
for (int i = 0; i < students.size(); i++) {
cout << "学号：" << students[i].getId() << " 姓名：" << students[i].getName() << " 性别：" << students[i].getGender() << endl;
vector<double> grades = students[i].getGrades();
cout << "成绩：";
for (int j = 0; j < grades.size(); j++) {
cout << grades[j] << " ";
}
cout << "平均成绩：" << students[i].getAverage() << endl;
}
}

double getCourseAverage(int courseIndex) {
double sum = 0;
for (int i = 0; i < students.size(); i++) {
vector<double> grades = students[i].getGrades();
sum += grades[courseIndex];
}
return sum / students.size();
}

double getCourseHighest(int courseIndex) {
double highest = 0;
for (int i = 0; i < students.size(); i++) {
vector<double> grades = students[i].getGrades();
if (grades[courseIndex] > highest) {
highest = grades[courseIndex];
}
}
return highest;
}

double getCourseLowest(int courseIndex) {
double lowest = 100;
for (int i = 0; i < students.size(); i++) {
vector<double> grades = students[i].getGrades();
if (grades[courseIndex] < lowest) {
lowest = grades[courseIndex];
}
}
return lowest;
}

void printCourseInfo(int courseIndex) {
cout << "课程" << courseIndex << "的平均成绩：" << getCourseAverage(courseIndex) << endl;
cout << "课程" << courseIndex << "的最高分：" << getCourseHighest(courseIndex) << endl;
cout << "课程" << courseIndex << "的最低分：" << getCourseLowest(courseIndex) << endl;
}

void searchStudent(string keyword) {
for (int i = 0; i < students.size(); i++) {
if (students[i].getId() == stoi(keyword) || students[i].getName() == keyword) {
cout << "学号：" << students[i].getId() << " 姓名：" << students[i].getName() << " 性别：" << students[i].getGender() << endl;
vector<double> grades = students[i].getGrades();
cout << "成绩：";
for (int j = 0; j < grades.size(); j++) {
cout << grades[j] << " ";
}
cout << "平均成绩：" << students[i].getAverage() << endl;
}
}
}
};