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約数を高速に計算する方法

Last updated at Posted at 2021-03-01

とりま備忘録.高速に計算する方法


std::vector<long long> divisor(long long n) {
    std::vector<long long> ret;
    for (long long i = 1; i * i <= n; i++) {
        if (n % i == 0) {
            ret.push_back(i);
            if (i * i != n) ret.push_back(n / i);
        }
    }
    sort(ret.begin(), ret.end()); // 昇順に並べる
    return ret;
}

これによって,O(√N)で計算できるそう.楽やね~

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