c++

primes_generator

    struct generator {
        using array = std::vector<int>;
        static array gen(int num) {
            array primes{2};
            array visited(num, 0);
            for (int i=3; i<num; i+=2) {
                if (visited[i] == 0 && i % primes.back() != 0) {
                    primes.push_back(i);
                    for (int n=i; n<num; n+=i) {
                        visited[n] = 1;
                    }
                }
            }
            return primes;
        }
        static void show(int num) {
            auto a = std::chrono::steady_clock::now();
            auto primes = gen(num);
            auto b = std::chrono::steady_clock::now();
            auto delta = std::chrono::duration_cast<std::chrono::microseconds>(b-a);
            printf("%d, %zu, %lld us, (last 10): ", num, primes.size(), delta.count());
            for (auto i = primes.rbegin(); i != primes.rbegin() + 10 && i != primes.rend(); ++i) {
                printf("%d ", *i);
            }
            puts("\n");
        }
    };

    int main() {
        puts("\n");
        generator::show(40);
        generator::show(400);
        generator::show(4000);
        generator::show(40000);
        generator::show(400000);
        generator::show(4000000);
        generator::show(40000000);
        generator::show(400000000);
        return 0;
    }