binary search

#include <iostream>
#include <sstream>

using namespace std;

struct Student
{
    string ime, prezime;

};

int binarnaKraj(Student niz[], int maxGr, int vel, Student novi, int minGr=0)
{
    if(minGr>maxGr)
        return -1;
    else
    {

        if(novi.ime[0] == niz[(minGr+maxGr)/2].ime[0]  && novi.prezime == niz[(minGr+maxGr)/2].prezime)
        {
            if((minGr + maxGr)/2 != vel && niz[((minGr+maxGr)/2)+1].ime[0]== novi.ime[0] && novi.prezime == niz[((minGr+maxGr)/2)+1].prezime)
                return binarnaKraj(niz, maxGr+1,vel, novi, minGr);
            else
                return (minGr+maxGr)/2;
        }

        else if(novi.ime[0] < niz[(minGr+maxGr)/2].ime[0] && novi.prezime==niz[(minGr+maxGr)/2].prezime)
        {
            return binarnaKraj(niz, (minGr+maxGr)/2-1, vel,novi, minGr);
        }

        else
        {
            return binarnaKraj(niz, maxGr,vel, novi, (minGr+maxGr)/2+1);
        }
    }

}

int binarnaPocetak(Student niz[], int maxGr, Student novi, int minGr=0)
{

    if(minGr>maxGr)
        return -1;

        else
    {
        if(novi.ime[0] == niz[(minGr+maxGr)/2].ime[0]  && novi.prezime == niz[(minGr+maxGr)/2].prezime)
        {
            if((minGr + maxGr)/2 != 0 && niz[((minGr+maxGr)/2)-1].ime[0]== novi.ime[0] && novi.prezime == niz[((minGr+maxGr)/2)-1].prezime)

                return binarnaPocetak(niz, maxGr, novi, minGr-1);
            else
                return (minGr+maxGr)/2;

        }

        else if(novi.ime[0] < niz[(minGr+maxGr)/2].ime[0] && novi.prezime==niz[(minGr+maxGr)/2].prezime)
        {
            return binarnaPocetak(niz, (minGr+maxGr)/2-1, novi, minGr);
        }

        else
        {

            return binarnaPocetak(niz, maxGr, novi, (minGr+maxGr)/2+1);
        }
    }

}

std::string PrebaciUString(int N) {
    std::ostringstream tok;

    tok << N;

    return tok.str();
}

string dajEmail(Student studenti[], int brojStudenata, Student novi)
{
    int ind1= binarnaKraj(studenti, brojStudenata, brojStudenata, novi);
    int ind2= binarnaPocetak(studenti, brojStudenata, novi);
    int broj=ind1-ind2+1;
    if(ind2==0)
    broj++;


    cout << ind1 << ind2;


    char s1=novi.ime[0];
    string s2=novi.prezime;

     string s3 = PrebaciUString(broj);

    string s="";
    s+=s1;
    s+=s2;
    s+=s3;
    return s;
}

int main()
{
    Student niz[3]= {{"Ae", "aaa"}, {"Adela", "Vukas"},{"Adijata", "Vukas"}};

    cout << dajEmail(niz, 3 , {"Amela", "Vukas"});

    return 0;
}