Dev - C++ - Vector de elementos variables sin especificar cantidad

#include <iostream>

using namespace std;

int main()

{

    int N;

    cout << "\nNumero de elementos a guardar: ";

    cin >> N;

    int arr[N];

    return 0;

}

#include <iostream>

#include <cctype>

using namespace std;

int main()

{

    int arr[100] = { 0 };

    int j = 0;

    char a;

    cout << "\nIntroduce numeros (escribe un punto para terminar .): ";

    do{

        cin >> a;

        if( isdigit( a ) )

            arr[j] = a - 48;

        else

            break;

        j++;

    }while( !ispunct( a ) );

    cout << endl;

    for( int i = 0; i < 100; i++ ){

        cout << arr[i] << " ";

    }

    cout << endl;

    return 0;

}

#include <cstddef>   // size_t

#include <iostream>  // cout, cin

#include <sstream>   // stringstream

#include <string>    // string, getline()

using namespace std;

int main() {

    const size_t kSize = 100;

    int numeros[kSize] = { };

    string entrada;

    getline(cin, entrada);

    stringstream ss(entrada);

    size_t i = 0;

    while (i < kSize) {

        int numero;

        ss >> numero;

        if (ss.fail()) {

            ss.clear();

            break;

        }

        numeros[i] = numero;

        ++i;

    }

    for (size_t j = 0; j < kSize; ++j) {

        cout << numeros[j] << "  ";

    }

    cout << '\n';

    return 0;

}