Access Struct in C++?

Question

I have a problem in c++ the teacher asking us to display a field of structures that contains n=100 students. Is this the right way to do it ?

#include <iostream>
#include <math.h>

using namespace std;

struct Students{
    string name;
    int id;
    int mark1;
    int mark2;
    int mark3;
};

int main(){
    int T[3];
    int i;

    for(i=0;i<=3;i++){
        T[i] = i;
    }
    for(i=0;i<=3;i++){
        Students T[i];
        cout<< T[i].name<<endl;
        cout<< T[i].id<<endl;
        cout<< T[i].mark1<<endl;
        cout<< T[i].mark2<<endl
        cout<< T[i].mark3<<endl;
    }
    return 0;
}

Answer 1

The program does not make sense. You should either declare an array of type Students or use some other standard container as for example std::vector<Students>. And after the container will be defined you have to enter values for each element.

For example

const size_t N = 100;
Students students[N];

for ( size_t i = 0; i < N; i++ )
{
    std::cout << "Enter name of student " << i + 1 << ": ";
    std::cin >> students[i].name;
    // ...
}

Or

#include <vector>

//...

const size_t N = 10;
std::vector<Students> students;
students.reserve( N );

for ( size_t i = 0; i < N; i++ )
{
    Students s;
    std::cout << "Enter name of student " << i + 1 << ": ";
    std::cin >> s.name;
    // ...
    students.push_back( s );
}

To display the all ready filled container (an array or a vector) you can for example the range-based for statement

for ( const Students & s : students )
{
    std::cout << "Name " << s.name << std::endl;
    //...
}

or an ordinary for loop

for ( size_t i = 0; i < N; i++ )
{
    std::cout << "Name " << students[i].name << std::endl;
    //...
}

For a vector the condition of the loop will look

for ( std::vector<Students>::size_type i = 0; i < students.size(); i++ )
//...

Answer 2

    int T[3];
    int i;

    for(i=0;i<=3;i++){
        T[i] = i;
    }

Above code snippet correct as follows:

    Students T[3]; //Here you are creating only 3 students  record, 
                   //if it needed 100 change 3 to 100 and change
                   // boundary change in below for loop also
    for(int i=0;i<=3;i++){
        T[i].name=<>;
        T[i].id=<>;
      // upadte your array of structure students as follows: ....

    }