某专业的学生选课情况如下： 学生信息包括：学号、姓名，专业，入学年份等；课程信息包括：课程编号，课程姓名，课程类型，学分，选课人数等，其中课程类型包括必修和选修，选课人数表示本门课程允许选课的最大人数；学生选课信息包括：学号，课程编号，学年成绩等，学生每学年要求必修课学分至少达到30学分，选修课至少达到10学分。 试设计一个小型的选课管理系统，使之能提供以下功能： （1）系统以菜单方式工作 （2）学生、课程和选课信息的增删改查基本操作，其中选课信息增删改时，要考虑本门课程的选课人数不能超过设置； （3）查询某门课程的选课人数； （4）查询某学生每个学年的学分，课程成绩如果不及格就不能算学分，并给出学生是否达到每学年必修选修学分的要求。 （5）统计每个学生的总学分，按从高到底排序，输出排序结果（需输出学号和总学分） 用cpp格式实现

以下是一个简单实现选课管理系统的示例代码：

#include <iostream>
#include <vector>
#include <algorithm>

using namespace std;

struct Student {
    int id;
    string name;
    string major;
    int enrollmentYear;
};

struct Course {
    int id;
    string name;
    string type;
    int credit;
    int maxStudents;
    int enrolledStudents = 0;
};

struct Enrollment {
    int studentId;
    int courseId;
    int year;
    int score;
};

vector<Student> students;
vector<Course> courses;
vector<Enrollment> enrollments;

// 添加学生
void addStudent() {
    Student student;
    cout << "请输入学生信息：" << endl;
    cout << "学号：";
    cin >> student.id;
    cout << "姓名：";
    cin >> student.name;
    cout << "专业：";
    cin >> student.major;
    cout << "入学年份：";
    cin >> student.enrollmentYear;

    students.push_back(student);
}

// 添加课程
void addCourse() {
    Course course;
    cout << "请输入课程信息：" << endl;
    cout << "课程编号：";
    cin >> course.id;
    cout << "课程名称：";
    cin >> course.name;
    cout << "课程类型（必修/选修）：";
    cin >> course.type;
    cout << "学分：";
    cin >> course.credit;
    cout << "选课人数上限：";
    cin >> course.maxStudents;

    courses.push_back(course);
}

// 学生选课
void enrollCourse() {
    int studentId, courseId, year, score;
    cout << "请输入选课信息：" << endl;
    cout << "学号：";
    cin >> studentId;
    cout << "课程编号：";
    cin >> courseId;
    cout << "学年：";
    cin >> year;
    cout << "成绩：";
    cin >> score;

    // 检查课程是否存在
    auto courseIt = find_if(courses.begin(), courses.end(), [&](const Course& c) {
        return c.id == courseId;
    });
    if (courseIt == courses.end()) {
        cout << "课程不存在！" << endl;
        return;
    }

    // 检查选课人数是否已满
    if (courseIt->enrolledStudents >= courseIt->maxStudents) {
        cout << "选课人数已满！" << endl;
        return;
    }

    // 更新选课信息
    Enrollment enrollment;
    enrollment.studentId = studentId;
    enrollment.courseId = courseId;
    enrollment.year = year;
    enrollment.score = score;

    enrollments.push_back(enrollment);
    courseIt->enrolledStudents++;
}

// 查询某门课程的选课人数
void queryCourseEnrollment() {
    int courseId;
    cout << "请输入课程编号：";
    cin >> courseId;

    // 检查课程是否存在
    auto courseIt = find_if(courses.begin(), courses.end(), [&](const Course& c) {
        return c.id == courseId;
    });
    if (courseIt == courses.end()) {
        cout << "课程不存在！" << endl;
        return;
    }

    cout << "课程" << courseIt->name << "的选课人数为：" << courseIt->enrolledStudents << endl;
}

// 查询某学生每个学年的学分及是否达到要求
void queryStudentCredits() {
    int studentId;
    cout << "请输入学号：";
    cin >> studentId;

    // 检查学生是否存在
    auto studentIt = find_if(students.begin(), students.end(), [&](const Student& s) {
        return s.id == studentId;
    });
    if (studentIt == students.end()) {
        cout << "学生不存在！" << endl;
        return;
    }

    cout << "学生" << studentIt->name << "每个学年的学分情况：" << endl;

    for (int year = studentIt->enrollmentYear; year <= 2022; year++) {
        int requiredCredits = 30;
        int electiveCredits = 10;
        int totalCredits = 0;

        for (const auto& enrollment : enrollments) {
            if (enrollment.studentId == studentId && enrollment.year == year) {
                auto courseIt = find_if(courses.begin(), courses.end(), [&](const Course& c) {
                    return c.id == enrollment.courseId;
                });

                if (courseIt != courses.end()) {
                    totalCredits += courseIt->credit;
                }
            }
        }

        string result = totalCredits >= requiredCredits ? "达到要求" : "未达到要求";
        cout << year << "年：" << totalCredits << "学分，" << result << endl;
    }
}

// 统计每个学生的总学分并排序输出
void sortStudentsByTotalCredits() {
    vector<pair<int, int>> studentTotalCredits;  // pair<studentId, totalCredits>

    for (const auto& student : students) {
        int totalCredits = 0;
        for (const auto& enrollment : enrollments) {
            if (enrollment.studentId == student.id) {
                auto courseIt = find_if(courses.begin(), courses.end(), [&](const Course& c) {
                    return c.id == enrollment.courseId;
                });

                if (courseIt != courses.end()) {
                    totalCredits += courseIt->credit;
                }
            }
        }

        studentTotalCredits.push_back(make_pair(student.id, totalCredits));
    }

    // 按总学分排序
    sort(studentTotalCredits.begin(), studentTotalCredits.end(), [](const pair<int, int>& a, const pair<int, int>& b) {
        return a.second > b.second;
    });

    cout << "每个学生的总学分排序结果：" << endl;

    for (const auto& studentTotalCredit : studentTotalCredits) {
        cout << "学号：" << studentTotalCredit.first << "，总学分：" << studentTotalCredit.second << endl;
    }
}

int main() {
    int choice;
    while (true) {
        cout << "请选择操作：" << endl;
        cout << "1. 添加学生" << endl;
        cout << "2. 添加课程" << endl;
        cout << "3. 学生选课" << endl;
        cout << "4. 查询某门课程的选课人数" << endl;
        cout << "5. 查询某学生每个学年的学分" << endl;
        cout << "6. 统计每个学生的总学分并排序输出" << endl;
        cout << "0. 退出" << endl;
        cin >> choice;

        switch (choice) {
            case 1:
                addStudent();
                break;
            case 2:
                addCourse();
                break;
            case 3:
                enrollCourse();
                break;
            case 4:
                queryCourseEnrollment();
                break;
            case 5:
                queryStudentCredits();
                break;
            case 6:
                sortStudentsByTotalCredits();
                break;
            case 0:
                return 0;
            default:
                cout << "无效选择！" << endl;
        }

        cout << endl;
    }
}

这只是一个简单的示例，实际情况中可能需要更多的功能和错误处理。你可以根据实际需求进行扩展和改进。