[C++] Struct sort

[minghags]

Hello can anyone help me with sorting this struct by name and surname? Ive done like this and it doesn't sort it.

Thanks

Code:

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



struct student
{
    int st_studenta;
    string vpisna;
    string ime;
    string priimek;
};
student vpis(int st_studenta)
{
    student student;
    string vpisna,ime,priimek;
    cout<<endl<<"Vnesite vpisno številko študenta: ";
    cin>>vpisna;
    cout<<endl<<"Vnesite ime študenta: ";
    cin>>ime;
    cout<<"Vnesite priimek študenta: ";
    cin>>priimek;
    student.st_studenta=st_studenta+1;
    student.vpisna=vpisna;
    student.ime=ime;
    student.priimek=priimek;
    return student;
}
void izpis(student student)
{
    cout<<endl<<"St. študenta: "<<student.st_studenta;
    cout<<endl<<"Vpisna: "<<student.vpisna<<endl;
    cout<<endl<<"Ime: "<<student.ime<<endl;
    cout<<endl<<"Priimek: "<<student.priimek<<endl;
}

bool sort_by_name( const student & lhs, const student & rhs )
{
    return lhs.ime < rhs.ime;
}
bool sort_by_age( const student & lhs, const student & rhs )
{
    return lhs.priimek < rhs.priimek;
}

int main()
{
    int st_studentov=0;
    student seznam_student[50];
    int meni;
    do
    {
        cout<<"-------MENU-------------"<<endl;
        cout<<"________________________"<<endl;
        cout<<"1. Vnos študenta        "<<endl;
        cout<<"2. Izpis študentov      "<<endl;
        cout<<"3. Sortiranje študentov "<<endl;
        cout<<"4. Najdi študenta       "<<endl;
        cout<<"0. Izhod                "<<endl;
        cout<<"========================"<<endl;
        cin>>meni;
        
        if(meni==1)
        {
            seznam_student[st_studentov]=vpis(st_studentov);
            st_studentov++;
        }
        if(meni==2)
        {
            for(int a=0;a<st_studentov;a++)
            {
                izpis(seznam_student[a]);
            }
        }
        if(meni==3)
        {
            std::vector<student> people;
            std::sort( people.begin(), people.end(), sort_by_name );
            std::sort( people.begin(), people.end(), sort_by_age );
        }
    }while(meni!=0);
    return 0;
}

[Labdabeta]

I do not know much about std::sort, but it is easy enough to sort this array manually. I would suggest using an insertion sort for each student entered, since it works really fast if the array is mostly sorted. Here is a sample implementation:

//This function will sort the vector of students
//It works REALLY fast on data that is mostly sorted
//  as such it should be called on the data every time
//  a new piece of data is entered.
void insertionSort(vector<student> &students, bool (*areInOrder)(student&,student&))
{
    for (int i=0; i<students.size(); ++i)
    {
        student thisStudent=students[i];//this will help make swapping faster
        int x=i-1;//this stores the index we want to swap to
        bool done=false;
        while (!done)
        {
            if (!areInOrder(student[x],students[i]))
            {
                //we will need to swap them
                students[x+1]=students[x];
                --x;
                if (x<0)
                {
                    //we must be done!
                    bone=true;
                }
            }
        }
        students[x+1]=thisStudent;
    }
}

Also the problem may be in your sort_by_name function. The std::string's > operator might not sort in ascending order, but may instead sort by location in memory. Perhaps you will have to wright your own? (compare ASCII values until you find a difference?)

[Lerner]

>>sorting this struct by name and surname

If surname is listed first, like so:
Smith, John
then comparing the full string should sort by surname and then by first name.

>>student student;
That's not a good idea, it it's even legal. Never name an object the same name as the class name.

[jaskij]

You do not populate the people vector.

This should work correctly, if memory serves:

std::sort(seznam_student,seznam_student+st_studentov,sort_by_name)

Or just use a vector from the beginning:

std::vector<student> seznam_student;

if(meni==1)
{
	seznam_student.push_back(vpis(st_studentov));
	st_studentov++;
}
if(meni==2)
{
for(int a=0;a<st_studentov;a++)
{
	izpis(seznam_student[a]);
}
}
if(meni==3)
{
	std::vector<student> people;
	std::sort( people.begin(), people.end(), sort_by_name );
	std::sort( people.begin(), people.end(), sort_by_age );
}