[Lekcja 18] Błąd przy wypisywaniu liczb

#include <iostream>
#include <ctime>
#include <cstdlib>

using namespace std;

/* draw random numbers */
int randomNumber( int a, int b ) {
    int number = rand() %( b - a + 1 ) + a;
    return number;
}

/* assign numbers to container array */
void drawNumbers( int a, int b, int container[], int counter ) {
    int i = 0;
    do {
        container[ i ] = randomNumber( a, b );
        i++;
    } while( i < counter );
   
}

void displayAllNumbers( int container[], int counter ) {
    int i = 0;
    do
    {
        cout << i << ". " << container[ i ] << "\t";
        i++;
    } while( i < counter );
   
}

void addition( int container[], int counter ) {
    int i = 0;
    int sum;
    cout << "\nAddition..." << endl;
    do {
        sum += container[ i ];
        cout << i << ". " << sum << "\t";
        i++;
    } while( i < counter );
   
    cout << "\nSum: " << sum << endl;
}

int main() {
    srand( time( NULL ) );
    int containerForNum[ 999 ];
    int initialNum = 4;
    int finalNum = 10;
    int quantity = 999;
   
    drawNumbers( initialNum, finalNum, containerForNum, quantity );
    displayAllNumbers( containerForNum, quantity );
    addition( containerForNum, quantity );
    return 0;
}