Question

对于我的GroupPicker程序，我需要允许class group为随机生成的每个数字分配无限数量的插槽，这些数字分配给每个输入的学生。代码：

#include <iostream>
#include <string>
#include <fstream>
#include <cstdlib>
#include <time.h>

using namespace std;

class student
{
    int m_studentNumber;
public:
    string nameFirst;
    string nameLast;
    string nameFull;
    int getStudentNumber() { return m_studentNumber; }
    void setStudentNumber(int studentNumber) { m_studentNumber = studentNumber; }
};

class group
{
public:
};

ostream& operator<<(ostream& os, const student& s)
{
     return os << s.nameFirst << ' ' << s.nameLast;
}

student typeName()
{
    student bar;
    cout << "Type in a student's first name: ";
    cin >> bar.nameFirst;
    cout << "Type in that student's last name: ";
    cin >> bar.nameLast;
    cout << "\n";
    bar.nameFull = bar.nameFirst + " " + bar.nameLast;
    return bar;
}

void displayStudents(student listOfStudents[50], int studentHeadCount)
{
    for (int i = 0; i < studentHeadCount; i++)
    {
        cout << listOfStudents[i].nameFull << endl;
        cout << listOfStudents[i].getStudentNumber() << endl;
        cout << "\n";
    }
}

void options()
{

    cout << "Select what you want to do:\n";
    cout << "1) Exit application\n";
    cout << "2) Enter a Student\n";
    cout << "3) Display Students\n";
    cout << "4) Display Groups\n";
    cout << "5) Output groups as text file\n";
    cout << "\n";
}

int main()
{
    student allStudents[50]; // Having 50 students alone is ridiculous
    bool endProg = 0;
    int maxStudents;
    int studentsPerGroup;
    int optionSelect;
    int studentHeadCount = 0;
    int remainder;
    int numberOfGroups;
    cout << "GroupPicker 1.0\n";    
    cout << "How many students are in the class?\n" << "(Note: You cannot have more than 50 in this program)\n";
    cin >> maxStudents;
    if (maxStudents > 50)
    {
        cerr << "Too many students! Exiting program...\n";
        system("PAUSE");
        exit(1);
    }
    cout << "How many students per group?\n";
    cin >> studentsPerGroup;
    if (studentsPerGroup >= maxStudents)
    {
        cerr << "You're kidding, right?\n" << "Exiting program...\n";
        system("PAUSE");
        exit(1);
    }
    while (endProg == 0) {
        options();
        cin >> optionSelect;
        switch (optionSelect) {
            case 1:
                endProg = 1;
                break;
            case 2:
            {
                if (studentHeadCount == maxStudents)
                {
                    cerr << "You can't enter more than " << maxStudents << " students\n";
                }
                else
                {
                    allStudents[studentHeadCount] = typeName();
                    allStudents[studentHeadCount].setStudentNumber(studentHeadCount);
                    studentHeadCount++;
                }
                break;
            }
            case 3:
                cout << "Current list of students:\n\n";
                displayStudents(allStudents, studentHeadCount);
                break;
            case 4:
            {
                if (studentHeadCount < studentsPerGroup || studentHeadCount < maxStudents)
                {
                    cerr << "Invalid group parameters.\n" << "Returning to main menu...\n";
                    break;
                }
                else
                {
                cout << "Here are the groups:\n";
                numberOfGroups = maxStudents / studentsPerGroup;
                }
            }
            case 5:
            {
                cout << "Saving groups to file...\n";
                ofstream studentGroups;
                studentGroups.open("studentGroups.txt");
            }
        }
    }
}

我怎样才能在小组课程中拥有无限数量的变量，具体取决于每组学生的数量？

Answer 1

您不能拥有“无限”号码，因为您将受到可用内存的限制。但是，可以具有在编译时未指定的数字。将学生数组更改为学生矢量：

std::vector<student> allStudents;

Answer 2

您似乎正在寻找std::vector<student>等数据结构。

Answer 3

您实际上并不需要每组中有无数的学生。你真正需要的是每组中无限期的学生数量。为此，您可以在std::vector<student>类中使用任何标准容器，例如std::list<student>或group，或者替换group类。

一类中无限数量的成员变量？ C ++

3 个答案: