test/helloworld/eratosthenes-sieve.test.cpp

#define PROBLEM "http://judge.u-aizu.ac.jp/onlinejudge/description.jsp?id=ITP1_1_A"
#include <bits/stdc++.h>

#include "../../Math/Number-Theory/eratosthenes-sieve.hpp"
#include "../../Math/Number-Theory/is-prime.hpp"

constexpr int N = 1e4;
EratosthenesSieve sieve(N);

void test_isPrime() {
    for (int i = 0; i <= N; ++i) {
        assert(sieve.isPrime(i) == isPrime(i));
    }

    std::clog << __func__ << " : OK" << std::endl;
}

void test_minFactor() {

    const auto minFactor = [](int n) {
        if (n % 2 == 0) return 2;
        for (int i = 3; i < n; ++i)
            if (n % i == 0) return i;
        return -1;
    };

    for (int i = 2; i <= N; ++i) {
        if (sieve.isPrime(i)) {
            assert(sieve.minFactor(i) == i);
        } else {
            assert(sieve.minFactor(i) == minFactor(i));
        }
    }

    std::clog << __func__ << " : OK" << std::endl;
}

int main() {
    std::cout << "Hello World" << std::endl;

    test_isPrime();
    test_minFactor();

    return 0;
}

#line 1 "test/helloworld/eratosthenes-sieve.test.cpp"
#define PROBLEM "http://judge.u-aizu.ac.jp/onlinejudge/description.jsp?id=ITP1_1_A"
#include <bits/stdc++.h>

#line 5 "Math/Number-Theory/eratosthenes-sieve.hpp"

/**
 * @brief Eratosthenes-Sieve (エラトステネスの篩)
 * @see https://qiita.com/rsk0315_h4x/items/ff3b542a4468679fb409
 */
class EratosthenesSieve {
private:
    int m_size;
    std::vector<int> m_minFactor;

public:
    EratosthenesSieve() = default;

    //! [0, n] の範囲で篩を構築する
    explicit EratosthenesSieve(int n_)
        : m_size(n_ + 1)
        , m_minFactor(m_size) {
        std::iota(m_minFactor.begin(), m_minFactor.end(), 0);
        for (int i = 2; i * i < m_size; ++i) {
            if (m_minFactor[i] < i) continue;
            for (int j = i * i; j < m_size; j += i) {
                if (m_minFactor[j] == j) m_minFactor[j] = i;
            }
        }
        m_minFactor[0] = -1;
        if (n_ >= 1) m_minFactor[1] = -1;
    }

    bool isPrime(int x) const {
        assert(0 <= x && x < m_size);
        return m_minFactor[x] == x;
    }

    int minFactor(int x) const {
        assert(0 <= x && x < m_size);
        return m_minFactor[x];
    }
};
#line 3 "Math/Number-Theory/is-prime.hpp"

/**
 * @brief isPrime() (素数判定 $O(\sqrt n)$)
 */
constexpr bool isPrime(int64_t n) {
    if (n == 2) return true;
    if (n <= 1 || n % 2 == 0) return false;
    for (int64_t i = 3; i * i <= n; i += 2) {
        if (n % i == 0) return false;
    }
    return true;
}
#line 6 "test/helloworld/eratosthenes-sieve.test.cpp"

constexpr int N = 1e4;
EratosthenesSieve sieve(N);

void test_isPrime() {
    for (int i = 0; i <= N; ++i) {
        assert(sieve.isPrime(i) == isPrime(i));
    }

    std::clog << __func__ << " : OK" << std::endl;
}

void test_minFactor() {

    const auto minFactor = [](int n) {
        if (n % 2 == 0) return 2;
        for (int i = 3; i < n; ++i)
            if (n % i == 0) return i;
        return -1;
    };

    for (int i = 2; i <= N; ++i) {
        if (sieve.isPrime(i)) {
            assert(sieve.minFactor(i) == i);
        } else {
            assert(sieve.minFactor(i) == minFactor(i));
        }
    }

    std::clog << __func__ << " : OK" << std::endl;
}

int main() {
    std::cout << "Hello World" << std::endl;

    test_isPrime();
    test_minFactor();

    return 0;
}