Question

我从练习中得到了这段代码，我需要：

为学生添加他的姓名，身份证，教育程度和3个等级
修改学生成绩
删除学生
显示已批准学生的列表
显示受到重新照相的学生名单
显示完整列表

所以我使用向量完成了这个，这是我的代码：

int resp = 0;

vector<int> ids;
vector<string> names;
vector<string> levels;
vector<double> grades1;
vector<double> grades2;
vector<double> grades3;
vector<double> average;
vector<double> approved;
vector<double> repproved;

string name, level;
int id, elim, id_delete, i=0;
double grade=0, sum=0;

do {

    cout<<"######### OPTIONS MENU #########"<<"\n\n";

    cout<<"[1] Add a student"<<"\n";
    cout<<"[2] Add grades of a student"<<"\n";
    cout<<"[3] Modify grades of a student"<<"\n";   
    cout<<"[4] Delete a student"<<"\n";
    cout<<"[5] Show approved list"<<"\n";
    cout<<"[6] Show repproved list"<<"\n";
    cout<<"[7] Show the full list"<<"\n";
    cout<<"[8] Exit"<<"\n\n";

    cin>>resp;

    switch(resp) {
        case 1:
            cout<<"Enter the student's name: \n";
            cin.sync(); cin.clear();
            getline(cin, name);
            names.push_back(name);
            cout<<"Enter the student's id: \n";
            cin>>id;
            ids.push_back(id);
            cout<<"Enter the student's school level: \n";
            cin.sync(); cin.clear();
            getline(cin, level);
            levels.push_back(level);

            cout<<"Student added";

        break;
        case 2:
            cout<<"Enter the grade 1 of the student: \n";
            cin>>grade;
            grades1.push_back(grade);
            cout<<"Enter the grade 2 of the student: \n";
            cin>>grade;
            grades2.push_back(grade);
            cout<<"Enter the grade 3 of the student: \n";
            cin>>grade;
            grades3.push_back(grade);

            cout<<"Grades added";
        break;
        case 3:
            cout<<"Enter the student's id you wish to modify grades on: \n";
            cin>>id_delete;

            for(int i=0; i<ids.size(); i++) {
                if(id_delete==ids[i]) {
                    id_delete = i;
                    break;
                }
            }

            i=id_delete;
            cout<<"Enter the new grade 1 of the student: \n";
            cin>>grade;
            grades1[i] = grade;

            cout<<"Enter the new grade 2 of the student: \n";
            cin>>grade;
            grades2[i] = grade;

            cout<<"Enter the new grade 3 of the student: \n";
            cin>>grade;
            grades3[i] = grade;

            cout<<"Grades modified\n";

        break;
        case 4:
            cout<<"Enter the student's id you wish delete: \n";
            cin>>id_delete;

            for(int i=0; i<ids.size(); i++) {
                if(id_delete==ids[i]) {
                    id_delete = i;
                    break;
                }
            }

            ids.erase (ids.begin()+(id_delete-1));
            names.erase (names.begin()+(id_delete-1));
            levels.erase (levels.begin()+(id_delete-1));
            grades1.erase (grades1.begin()+(id_delete-1));
            grades2.erase (grades2.begin()+(id_delete-1));
            grades3.erase (grades3.begin()+(id_delete-1));

            cout<<"Student deleted\n";

        break;
        case 5:
            for(i = 0; i<ids.size(); i++) {
                average[i] = (grades1[i] + grades2[i] + grades3[i])/3;
            }

            for(i = 0; i<ids.size(); i++) {
                if(average[i] >= 7 && average[i] <= 10) {
                    approved[i] = average[i];
                } else {
                        repproved[i] = average[i];
                    }

            }

            for(i = 0; i<ids.size(); i++) {
                cout<<approved[i]<<endl;
            }
        break;
        case 6:
            for(i = 0; i<ids.size(); i++) {
                cout<<repproved[i]<<endl;
            }
        break;
        case 7:
            for(i = 0; i<ids.size(); i++) {
                cout<<approved[i]<<endl;
            }

            for(i = 0; i<ids.size(); i++) {
                cout<<repproved[i]<<endl;
            }

但是当选择选项5,6和7时，它会抛出“exercise.exe已停止工作”。

PS。我是C ++的初学者，这是我的第一个编程语言，遗憾的是......

Answer 1

发生崩溃是因为您访问超出其目的的多个向量的成员。

例如：

for(i = 0; i<ids.size(); i++) {
    average[i] = (grades1[i] + grades2[i] + grades3[i])/3;
}

在访问之前，您永远不会扩展平均数组。您确实扩展了成绩数组，但仅限于响应特定的用户输入。

每次添加学生时，您可能希望在所有阵列中添加条目。并且您应该在添加成绩之前询问学生ID，并将该案例视为修改。

更好的设计是使用从学生ID到结构的地图。

Answer 2

作为载体

vector<double> average;
vector<double> approved;
vector<double> repproved;

已创建，其大小为0，即它们不包含任何元素，因此当您第一次访问上述向量的元素为平均[i]时，这不是在内存中，所以您必须先将平均值插入，

average.push_back((grades1[i] + grades2[i] + grades3[i])/3);

不是

average[i] = (grades1[i] + grades2[i] + grades3[i])/3;

与其他两个向量相同

批准和重新批准

我希望你很清楚。

使用<vector>和cin以及for（）循环C ++

2 个答案: