courses

#include <iostream>
#include <vector>
#include <string>
#include <algorithm>

using std::cin;
using std::cout;
using std::endl;
using std::vector;
using std::string;

struct course
{
    int id = 0;
    vector<string> students{};
};

void fill_in(course* c)
{
    // заполняем структуру
    cout << "enter id: ";
    cin >> c->id;
    int count;
    cout << "enter count of students: ";
    cin >> count;
    for (int i = 0; i < count; i++)
    {
        string buf{};
        cout << "enter name of student: ";
        cin >> buf;
        c->students.push_back(buf);
    }
}

void show(const course& c)
{
    cout << "id: " << c.id << endl;
    cout << "students" << endl;
    for (string a: c.students)
        cout << a << endl;
}

int count(const course c)
{
    return c.students.size();
}

bool compare(const course &first, const course &second)
{
    // для убывания
    return first.students.size() > second.students.size();
}

int main()
{
    int numb = 0;
    cout << "enter number of courses: ";
    cin >> numb;
    vector<course> courses;
    for (int i = 0; i < numb; i++)
    {
        course *c = new course;
        fill_in(c);
        courses.push_back(*c);
    }
    cout << courses.size() << endl;
    std::sort(courses.begin() ,courses.end(), compare);
    for (course a: courses)
        show(a);
    system("pause");
    return 0;
}