C++学生管理系统课程分配问题修复及switch替代if-else场景说明

• 所有判断均为单个整型、字符型、枚举类型的等值判断场景，比如菜单选项选择、状态机状态跳转等，switch的分支逻辑比嵌套if-else更清晰易读
• 分支数量≥3个的等值判断场景，switch会被编译器优化为跳转表结构，执行效率远高于逐次条件判断的嵌套if-else
• 存在多个等值分支共用同一段处理逻辑的场景，可直接利用switch的case穿透特性简化代码，无需重复写多段相同的if判断逻辑
• 嵌套if-else层级超过3层时，用switch拆分逻辑可以大幅降低代码维护成本，减少漏写判断条件的概率

问题根因 #

当前代码的错误来自3个核心逻辑问题：

1. 没有单独存储公共课程列表，错误地把课程信息存在了学生结构体的info属性中，相当于每个学生自己存了一套课程数据，逻辑完全错误
2. 没有给每个学生存储自己选中的课程编号，输入的课程编号直接覆盖了全局变量n，只有最后一次输入的课程编号会被保留
3. 展示学生课程时，统一读取全局变量n的最后一次值取值，导致所有学生的课程都显示为最后一次输入的课程值

修复步骤 #

1. 单独定义Course类型的数组存储所有公共课程，不要和学生结构体绑定
2. 在Student结构体中新增int selectedCourseIdx属性，存储每个学生自己选中的课程下标
3. 录入学生选课信息时，把输入的课程编号转成下标后存入对应学生的selectedCourseIdx属性中，不要覆盖循环变量
4. 展示学生信息时，读取当前学生自身存储的selectedCourseIdx，到公共课程数组中取出对应课程信息展示

修复后完整代码 #

#include <iostream>
#include <string>
using namespace std;

struct Course {
    string CourseCode;
    string CourseName;
    string LecturerName;
};

struct Student {
    string StudentID;
    string StudentName;
    string Nickname;
    int selectedCourseIdx; // 存储学生选中的课程下标
};

void menu(void) {
    cout << "=================================" << endl;
    cout << "              MENU              " << endl;
    cout << "=================================" << endl;
    cout << "     1- Add new course" << endl;
    cout << "     2- Display course offered" << endl;
    cout << "     3- Add new students" << endl;
    cout << "     4- Display student list" << endl;
    cout << "     5- Modify student name" << endl;
    cout << "     6- Display student's name after modification" << endl;
    cout << "     7- Exit Program" << endl;
    cout << "=================================" << endl << endl;
}


int main()
{
    Course courses[2]; // 单独存储公共课程列表，最大2门
    Student students[5]; // 存储学生信息，最大5人
    int m, option, stuNo = 0, courNo = 0, opn;

    menu();
    cout << "Choose an option from the menu: ";
    cin >> option;

    while (option != 7)
    {
        if (option == 1) {
            cout << "\nHow many courses do you want to enter? [Maximum 2]: ";
            cin >> courNo;
            if (courNo > 2) courNo = 2;
            for (m = 0; m < courNo; m++) {
                cout << "\nEnter course " << m + 1 << " details: " << endl;
                cout << "Course Code: ";
                cin >> courses[m].CourseCode;
                cout << "Course Name: ";
                cin >> courses[m].CourseName;
                cout << "Lecturer Name: ";
                cin >> courses[m].LecturerName;
            }
        }

        else if (option == 2) {
            cout << "\nThe courses details you entered are:" << endl;
            for (m = 0; m < courNo; m++) {
                cout << "\nCourse " << m + 1 << ": " << endl;
                cout << "Course Code: " << courses[m].CourseCode << endl;
                cout << "Course Name: " << courses[m].CourseName << endl;
                cout << "Lecturer Name: " << courses[m].LecturerName << endl;
            }
        }

        else if (option == 3) {
            cout << "\nHow many students do you want to enter? [Maximum 5]: ";
            cin >> stuNo;
            if (stuNo > 5) stuNo = 5;
            for (m = 0; m < stuNo; m++) {
                cout << "\nEnter student " << m + 1 << " details: " << endl;
                cout << "ID: ";
                cin >> students[m].StudentID;
                cout << "Name: ";
                cin >> students[m].StudentName;
                cout << "Nickname: ";
                cin >> students[m].Nickname;
                cout << "Course number from the list: ";
                cin >> opn;
                students[m].selectedCourseIdx = opn - 1; // 转成数组下标存储
            }
        }

        else if (option == 4) {
            cout << "\nThe students details you entered are:" << endl;
            for (m = 0; m < stuNo; m++) {
                int cIdx = students[m].selectedCourseIdx;
                cout << "\nStudent " << m + 1 << ": " << endl;
                cout << "ID: " << students[m].StudentID << endl;
                cout << "Name: " << students[m].StudentName << endl;
                cout << "Nickname: " << students[m].Nickname << endl;
                if (cIdx >=0 && cIdx < courNo) {
                    cout << "Course " << courses[cIdx].CourseName<< endl;
                } else {
                    cout << "Course: Invalid course selection" << endl;
                }
            }
        }

        else if (option == 5) {
                cout << "\nEnter the student number that has been saved: ";
                cin >> opn;
                opn -= 1;
                if (opn >=0 && opn < stuNo) {
                    cout << "\nEnter the new name: ";
                    cin >> students[opn].StudentName;
                } else {
                    cout << "Invalid student number" << endl;
                }
        }

        else if (option == 6) {
            cout << "\nEnter the student number to query: ";
            cin >> opn;
            opn -= 1;
            if (opn >=0 && opn < stuNo) {
                cout << "Student "<< opn + 1 <<" new name: " << students[opn].StudentName << endl;
            } else {
                cout << "Invalid student number" << endl;
            }
        }

        else
            cout << "Invalid number! Please re-enter a choice from the menu." << endl;

        cout << "=====================================================" << endl;
        cout << "\nChoose an option from the menu: ";
        cin >> option;
    }

    cout << "End of program!" << endl;
    return 0;
}

内容的提问来源于stack exchange，提问作者ADAM78