How to add two more elements to four array elements?

Question

C++ / C#

in the commented line....

//добавить два элемента к массиву и посчитать кол-во элементов
#include <iostream>
#include <conio.h>

using namespace std;

int main() 
{   
    int rez;
  int arr[] = {1,8,3,2};	
    
    //arr[] += {7,8};               ????
    rez = sizeof(arr) / 4;          //кол-во элементов в массиве
    cout << rez << endl;            
    
    for (int i=0; i<=rez; i++)
        cout << arr[i] << ' ';
  
    getch();
    return 0;
}

Answer 1

Use std::vector.

#include <iostream>
#include <conio.h>
#include <vector>
using namespace std;

int main()
{
    int rez;
    int arr_src[] = {1,8,3,2};
    std::vector<int> arr(arr_src, arr_src + sizeof(arr_src)/sizeof(arr_src[0]));

    arr.push_back(7);
    arr.push_back(8);

    rez = arr.size();          //кол-во элементов в массиве
    cout << rez << endl;

    for (int i = 0; i < rez; i++)
        cout << arr[i] << ' ';

    getch();
    return 0;
}

You also have an error in the exit condition of the loop.

Answer 2

You need either an array with a margin (for example, for 6 places), or a dynamic one (for example, std::vector).
C++ is a rather low-level language, and the programmer himself can see where memory is dynamically allocated and where it is allocated in advance.