結果

問題 No.644 G L C C D M
コンテスト
ユーザー paruki
提出日時 2018-02-03 11:49:25
言語 C++14
(gcc 13.3.0 + boost 1.87.0)
結果
AC  
実行時間 5 ms / 2,000 ms
コード長 3,703 bytes
コンパイル時間 1,550 ms
コンパイル使用メモリ 173,388 KB
実行使用メモリ 5,376 KB
最終ジャッジ日時 2024-06-11 15:19:48
合計ジャッジ時間 2,195 ms
ジャッジサーバーID
（参考情報） 		judge4 / judge5
このコードへのチャレンジ
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ファイルパターン 結果
other AC * 27
権限があれば一括ダウンロードができます

ソースコード

diff # 

#define _USE_MATH_DEFINES
#include "bits/stdc++.h"
using namespace std;
#define FOR(i,j,k) for(int (i)=(j);(i)<(int)(k);++(i))
#define rep(i,j) FOR(i,0,j)
#define each(x,y) for(auto &(x):(y))
#define mp make_pair
#define MT make_tuple
#define all(x) (x).begin(),(x).end()
#define debug(x) cout<<#x<<": "<<(x)<<endl
#define smax(x,y) (x)=max((x),(y))
#define smin(x,y) (x)=min((x),(y))
#define MEM(x,y) memset((x),(y),sizeof (x))
#define sz(x) (int)(x).size()
#define RT return
#define vv(a,b,c,d) vector<vector<a> >(b,vector<a>(c,d))
#define vvv(a,b,c,d,e) vector<vector<vector<a> > >(b,vv(a,c,d,e))
using ll = long long;
using pii = pair<int, int>;
using vi = vector<int>;
using vll = vector<ll>;

template<int MOD>
class ModInt {
public:
    ModInt() :value(0) {}
    ModInt(long long val) :value((int)(val<0 ? MOD + val%MOD : val%MOD)) { }

    ModInt& operator+=(ModInt that) {
        value = value + that.value;
        if (value >= MOD)value -= MOD;
        return *this;
    }
    ModInt& operator-=(ModInt that) {
        value -= that.value;
        if (value<0)value += MOD;
        return *this;
    }
    ModInt& operator*=(ModInt that) {
        value = (int)((long long)value * that.value % MOD);
        return *this;
    }
    ModInt &operator/=(ModInt that) {
        return *this *= that.inverse();
    }
    ModInt operator+(ModInt that) const {
        return ModInt(*this) += that;
    }
    ModInt operator-(ModInt that) const {
        return ModInt(*this) -= that;
    }
    ModInt operator*(ModInt that) const {
        return ModInt(*this) *= that;
    }
    ModInt operator/(ModInt that) const {
        return ModInt(*this) /= that;
    }
    ModInt pow(long long k) const {
        if (value == 0)return 0;
        ModInt n = *this, res = 1;
        while (k) {
            if (k & 1)res *= n;
            n *= n;
            k >>= 1;
        }
        return res;
    }
    ModInt inverse() const {
        long long a = value, b = MOD, u = 1, v = 0;
        while (b) {
            long long t = a / b;
            a -= t * b;
            swap(a, b);
            u -= t * v;
            swap(u, v);
        }
        return ModInt(u);
    }
    int toi() const { return value; }

private:
    int value;
};
typedef ModInt<1000000007> mint;
ostream& operator<<(ostream& os, const mint& x) {
    os << x.toi();
    return os;
}

vector<bool> sieveFlags(int n) {
    vector<bool> f(n + 1);
    for (int i = 3; i <= n; i += 2)f[i] = true;
    for (int i = 3; (long long)i*i <= n; i += 2) {
        if (f[i])for (int j = i * 3; j <= n; j += i)f[j] = false;
    }
    if (n >= 2)f[2] = true;
    return f;
}

vector<int> enumMobius(const vector<bool> &sf) {
    int n = (int)sf.size();
    vector<int> res(n, 1);
    for (int i = 1; i < n; ++i)if (sf[i]) {
        for (int j = i; j < n; j += i) {
            res[j] *= -1;
        }
        long long power = (long long)i*i;
        for (long long j = power; j < n; j += power) {
            res[j] = 0;
        }
    }
    return res;
}

vector<int> enumTotient(int n) {
    vector<bool> sf = sieveFlags(n);
    vector<int> res(n + 1);
    vector<int> mobius = enumMobius(sf);
    for (int i = 1; i <= n; ++i) {
        int mob = mobius[i];
        if (mob == 0)continue;
        for (int j = i, k = 1; j <= n; j += i, ++k) {
            res[j] += mob*k;
        }
    }
    return res;
}

int main() {
    ios::sync_with_stdio(false);
    cin.tie(0);
    cout << fixed << setprecision(20);

    int N, M;
    cin >> N >> M;
    mint ans, A = 1;
    for (int i = 2; i <= N - 2; ++i)A *= i;
    N /= M;
    vi t = enumTotient(N);
    for (int i = 2; i <= N; ++i) {
        ans += A * 2 * t[i];
    }
    cout << ans << endl;
}
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