请用c++ stl实现以下内容：读取data数据，将其按照demo的格式放入demo中去，要求空出总分 客观题总分 主观题总分 ，demo中格式为考号 姓名 班级 总分 学校排名 班级排名 客观题总分 主观题总分 选择1 选择2 选择3 选择4 选择5 选择6 选择7 选择8 选择9 选择10 选择11 选择12 填空题 17 18 19 20 21 22，其中选择1 选择2 选择3 选择4 选择5 选择6 选择7 选择8 选择9 选择10 选择11 选择12 一行中的数据相加填入对应行的客观题总分中，填空17 填空18 填空19 填空20 填空21 填空22一行中的数据相加填入主观题总分中，之后每一行的主观题总分和客观题总分相加填入对应行的总分中，然后读取demo，将demo中的数据按照总分对不同班级进行排名和学校排名，按照班级依次以csv格式导出不同班级的表格，然后以csv格式导出学校的表格，完成后输出end。要求用c++ stl进行编写代码示例.

以下是一份C++ STL代码示例，实现上述要求：

#include <iostream>
#include <fstream>
#include <sstream>
#include <vector>
#include <map>
#include <algorithm>

using namespace std;

struct Student {
    string id;
    string name;
    string cls;
    int obj_score;
    int sub_score;
};

// 计算客观题总分
int calc_obj_score(const vector<int>& obj_scores) {
    int sum = 0;
    for (int score : obj_scores) {
        sum += score;
    }
    return sum;
}

// 计算主观题总分
int calc_sub_score(const vector<int>& sub_scores) {
    int sum = 0;
    for (int score : sub_scores) {
        sum += score;
    }
    return sum;
}

// 读取data文件，返回学生信息向量
vector<Student> read_data(const string& file_path) {
    vector<Student> students;
    ifstream ifs(file_path);
    string line;
    while (getline(ifs, line)) {
        istringstream iss(line);
        string id, name, cls;
        int obj1, obj2, obj3, obj4, obj5, obj6, obj7, obj8, obj9, obj10, obj11, obj12;
        int sub17, sub18, sub19, sub20, sub21, sub22;
        iss >> id >> name >> cls >> obj1 >> obj2 >> obj3 >> obj4 >> obj5 >> obj6 >> obj7 >> obj8 >> obj9 >> obj10 >> obj11 >> obj12 >> sub17 >> sub18 >> sub19 >> sub20 >> sub21 >> sub22;

        vector<int> obj_scores = {obj1, obj2, obj3, obj4, obj5, obj6, obj7, obj8, obj9, obj10, obj11, obj12};
        vector<int> sub_scores = {sub17, sub18, sub19, sub20, sub21, sub22};
        int obj_score = calc_obj_score(obj_scores);
        int sub_score = calc_sub_score(sub_scores);

        Student student = {id, name, cls, obj_score, sub_score};
        students.push_back(student);
    }
    return students;
}

// 计算排名并更新学生信息
void calc_rank(vector<Student>& students) {
    // 按总分排序
    sort(students.begin(), students.end(), [](const Student& a, const Student& b) {
        return a.obj_score + a.sub_score > b.obj_score + b.sub_score;
    });

    // 计算学校排名
    int rank = 1;
    int prev_score = -1;
    for (auto& student : students) {
        int score = student.obj_score + student.sub_score;
        if (score != prev_score) {
            rank = (prev_score == -1) ? 1 : rank + 1;
            prev_score = score;
        }
        student.id += "," + to_string(rank);
    }

    // 计算班级排名
    map<string, vector<Student>> cls_student_map;  // 班级 -> 学生列表
    for (auto& student : students) {
        cls_student_map[student.cls].push_back(student);
    }

    for (auto& item : cls_student_map) {
        vector<Student>& cls_students = item.second;
        sort(cls_students.begin(), cls_students.end(), [](const Student& a, const Student& b) {
            return a.obj_score + a.sub_score > b.obj_score + b.sub_score;
        });

        int rank = 1;
        int prev_score = -1;
        for (auto& student : cls_students) {
            int score = student.obj_score + student.sub_score;
            if (score != prev_score) {
                rank = (prev_score == -1) ? 1 : rank + 1;
                prev_score = score;
            }
            student.id += "," + to_string(rank);
        }
    }
}

// 将学生信息写入csv文件
void write_csv(const string& file_path, const vector<Student>& students) {
    ofstream ofs(file_path);
    ofs << "考号,姓名,班级,总分,学校排名,班级排名,客观题总分,主观题总分,选择1,选择2,选择3,选择4,选择5,选择6,选择7,选择8,选择9,选择10,选择11,选择12,填空题17,填空题18,填空题19,填空题20,填空题21,填空题22" << endl;
    for (auto& student : students) {
        ofs << student.id << "," << student.name << "," << student.cls << ",," << student.obj_score << ",," << student.sub_score << endl;
    }
}

int main() {
    vector<Student> students = read_data("data.txt");
    calc_rank(students);
    write_csv("school.csv", students);

    map<string, vector<Student>> cls_student_map;  // 班级 -> 学生列表
    for (auto& student : students) {
        cls_student_map[student.cls].push_back(student);
    }

    for (auto& item : cls_student_map) {
        string file_path = item.first + ".csv";
        vector<Student>& cls_students = item.second;
        write_csv(file_path, cls_students);
    }

    cout << "end" << endl;
    return 0;
}

注：代码为了简洁和易读性，省略了一些错误处理和异常处理。在实际应用中，建议对文件读取、字符串解析、数据处理等过程进行适当的错误处理和异常处理。