C++ struct questions, find maximal value in struct with float type data

Question

I try to find the maximum (higest) value from the input, but the value converted to other value. e.g when i put 3 for Mahasiswa.ipk it converted to 0, and Mahasiswa.nim converted to 6946913. How i can the real value shown in the ouput ?

using namespace std;

struct Mhs
{
    char nama[30];
    int nim[20];
    float ipk[2];
};

int BacaDataMhs(int N);
int TampilIpkMaxMin(int N);
int TampilIpkDua(int N); /// edited : I can use this function 

int main(int argc, char ** argv)
{
    int N;
    cout << "Input Value : "; cin >> N;
    TampilIpkMaxMin(N);
    int BacaDataMhs(int N);
}


int BacaDataMhs(int N)
{
    struct Mhs Mahasiswa[N];
    int i;

    for(i=0; i<N; i++)
    {
        cout << "NAMA : "; cin >> Mahasiswa[i].nama;
        cout << "NIM : "; cin >> Mahasiswa[i].nim[i];
        cout << "IPK : "; cin >> Mahasiswa[i].ipk[i];
        cout << endl;
    }
}

int TampilIpkMaxMin(int N)
{
    struct Mhs Mahasiswa[N];
    int i;
    int max=Mahasiswa[0].ipk[0];
    int min=Mahasiswa[0].ipk[0];
    int index_max=0;
    int index_min=0;

    for(i=0; i<N; i++)
    {
        if (max<Mahasiswa[i].ipk[i]) //calculate the higgest value
        {
            max=Mahasiswa[i].ipk[i];
            index_max=i;
        }
        if (min>Mahasiswa[i].ipk[i])
        {
            min=Mahasiswa[i].ipk[i];
            index_min=i;
        }
    }

    cout << "Nilai Tertinggi :" <<endl; //show the higgest value
    cout << "nama "<< Mahasiswa[index_max].nama << endl;
    cout << "nim "<< Mahasiswa[index_max].nim [index_max] << endl;
    cout << "ipk "<< Mahasiswa[index_max].ipk [index_max] << endl;

}
 int TampilIpkDua(int N) // i can use this function but not with int   TampilMhsMaxMin (int N )
{
 struct Mhs Mahasiswa[N];
int i;

    for(i=0; i<N; i++)
    {
        if (Mahasiswa[i].ipk[i]>2)
        {
            cout << "nama "<< Mahasiswa[i].nama << endl;
            cout << "nim "<< Mahasiswa[i].nim[i] << endl;
            cout << "ipk "<< Mahasiswa[i].ipk[i] << endl;
        }
    }

}

//edited

Answer 1

I still can't figure out the purpose of this exercise, but you don't seem to understand how scope or parameters work.

(I think) You want to have a collection of Mhs's, that get modified and read from in your functions. The easiest place to have define them is main, which is the common ancestor in the call graph.

Arrays with runtime bounds are not C++, although some compilers will accept them. std::vector is a much better container than an array for general use.

Don't put using namespace std in global scope, it will bring far too many names in.

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

struct Mhs
{
    std::string nama;
    int nim[20]; // Do you always need exactly 20 ints per nama?
    float ipk[2]; // Do you always need exactly 2 floats per nama?
};

void BacaDataMhs(std::vector<Mhs> &);
void TampilIpkMaxMin(std::vector<Mhs> &);

int main(int argc, char ** argv)
{
    int N;
    std::cout << "Input Value : "; std::cin >> N;

    // initialise N empty Mhs' into a vector called Mahasiswa
    std::vector<Mhs> Mahasiswa(N, Mhs{});

    // pass Mahasiswa to input function
    BacaDataMhs(Mahasiswa);

    // pass Mahasiswa to min_max output function
    TampilIpkMaxMin(Mahasiswa);
}

bool compareIpk(const Mhs & lhs, const Mhs & rhs)
{
    // find the largest of each sides ipk

    int left_max = *std::max_element(std::begin(lhs.ipk), std::end(lhs.ipk));
    int right_max = *std::max_element(std::begin(rhs.ipk), std::end(rhs.ipk));

    // compare them
    return left_max < right_max;
}

// simple text representation of an Mhs
std::ostream & operator <<(std::ostream & os, const Mhs & mhs)
{
    os << "nama "<< mhs.nama << std::endl;
    os << "nim {";
    for (int i = 0; i < 20; ++i)
    {
        os << mhs.nim[i];
    }
    os << '}' << std::endl;
    os << "ipk {";
    for (int i = 0; i < 2; ++i)
    {
        os << mhs.ipk[i];
    }
    os << '}' << std::endl;
    return os;
}

void BacaDataMhs(std::vector<Mhs> & Mahasiswa)
{
    for(Mhs & mhs : Mahasiswa)
    {
        std::cout << "NAMA : "; std::cin >> mhs.nama;
        std::cout << "NIM : "; 
        for(int i = 0; i < 20; ++i) {
            std::cin >> mhs.nim[i]; // Read in 20 ints
        }
        std::cout << "IPK : ";
        for(int i = 0; i < 2; ++i) {
            std::cin >> mhs.ipk[i]; // Read in 2 floats
        }

        std::cout << std::endl;
    }
}

void TampilIpkMaxMin(std::vector<Mhs> & Mahasiswa)
{
    using It = std::vector<Mhs>::iterator;
    std::pair<It, It> Mahasiswa_max = std::minmax_element(Mahasiswa.begin(), Mahasiswa.end(), compareIpk);

    std::cout << "Nilai Tertinggi :" << std::endl; //show the highest value
    std::cout << *Mahasiswa_max.first;

    std::cout << "Lowest Value :" << std::endl; //show the lowest value
    std::cout << *Mahasiswa_max.second;

}