c_cpp Eratosthenes的Prime Sieve

Posted 2021-05-14

bool isp[N];
vector<int> primes;
void sieve() {
    for (int i = 0; i < N; i++)
        isp[i] = true;
    isp[0] = isp[1] = false;
    for (int i = 4; i < N; i += 2)
        isp[i] = false;
    for (int i = 3; i * i < N; i += 2)
        if (isp[i])
            for (int j = i + i; j < N; j += i)
                isp[j] = false;
}