에라체

 

 

static ArrayList<Integer> Sieve_Of_Eratosthenes (int N)
{
    ArrayList<Integer> al = new ArrayList<>();
    boolean[] check = new boolean[N+1];

    for (int i=2; i*i<=N; i++)
    {
        if ( check[i] == false )
        {
            for (int j=i*i; j<=N; j+=i)
                check[j] = true;
        }
    }

    for (int i=2; i<=N; i++)
    {
        if ( check[i] == false )
            al.add(i);
    }

    return al;
}