Optimise a code of random number with no repetition in C

I do a code that will display to the screen 10 random numbers with no repetitions. I want to know if we can optimize the code or if you have a better and simple way in order to do this request. Thanks !!

int main(){
int nbr = 0; srand(time(NULL));
int arr[10], i, j, flag;

for (i = 0; i < 10; i++)
{
    do
    {
        nbr = rand() % 10 + 1;
        flag = 1;
        for (j = 0; j  < i; j ++)
        {
            if (nbr == arr[j])
            {
                flag = 0;
                break;
            }
        }

    } while (!flag);
    arr[i] = nbr;
}

for (i = 0; i < 10; i++)
{
    printf("%5d", arr[i]);
}



system("PAUSE");
return 0;
}