用C++语言面向对象的编程思维写学生成绩管理系统，功能包括学生信息的添加、查找、删除、导出、显示、保存等，用简单易懂的代码编写

好的，下面是一个简单易懂的 C++ 学生成绩管理系统的代码：

#include <iostream>
#include <fstream>
#include <vector>
#include <string>

using namespace std;

// 学生类
class Student {
public:
    Student(string name, string id, double score) {
        this->name = name;
        this->id = id;
        this->score = score;
    }

    string getName() const { return name; }
    string getId() const { return id; }
    double getScore() const { return score; }

private:
    string name;
    string id;
    double score;
};

// 学生管理类
class StudentManager {
public:
    // 添加学生
    void addStudent(Student student) {
        students.push_back(student);
    }

    // 查找学生
    vector<Student> findStudent(string id) {
        vector<Student> foundStudents;
        for (auto student : students) {
            if (student.getId() == id) {
                foundStudents.push_back(student);
            }
        }
        return foundStudents;
    }
    
    // 删除学生
    void deleteStudent(string id) {
        for (auto it = students.begin(); it != students.end(); ) {
            if (it->getId() == id) {
                it = students.erase(it);
            } else {
                ++it;
            }
        }
    }

    // 导出学生信息
    void exportStudentInfo(string filename) {
        ofstream fout(filename);
        for (auto student : students) {
            fout << student.getName() << " " << student.getId() << " " << student.getScore() << endl;
        }
        fout.close();
    }

    // 显示学生信息
    void showStudentInfo() {
        for (auto student : students) {
            cout << student.getName() << " " << student.getId() << " " << student.getScore() << endl;
        }
    }

    // 保存学生信息
    void saveStudentInfo(string filename) {
        ofstream fout(filename);
        for (auto student : students) {
            fout << student.getName() << " " << student.getId() << " " << student.getScore() << endl;
        }
        fout.close();
    }

private:
    vector<Student> students;
};

// 主函数
int main() {
    StudentManager manager;

    // 添加学生
    manager.addStudent(Student("张三", "20190101", 90.5));
    manager.addStudent(Student("李四", "20190102", 85.0));
    manager.addStudent(Student("王五", "20190103", 92.0));

    // 查找学生
    vector<Student> foundStudents = manager.findStudent("20190102");
    if (!foundStudents.empty()) {
        cout << "查找到的学生信息：" << endl;
        for (auto student : foundStudents) {
            cout << student.getName() << " " << student.getId() << " " << student.getScore() << endl;
        }
    } else {
        cout << "未找到该学生信息！" << endl;
    }

    // 删除学生
    manager.deleteStudent("20190103");

    // 导出学生信息
    manager.exportStudentInfo("students.txt");

    // 显示学生信息
    manager.showStudentInfo();

    // 保存学生信息
    manager.saveStudentInfo("students.txt");
    
    return 0;
}

以上代码实现了学生成绩管理系统的基本功能，可以添加、查找、删除、导出、显示、保存学生信息。注意，上述代码中并没有进行输入数据的处理，你需要自己添加相应的代码实现。