結果

問題 No.2351 Butterfly in Summer
ユーザー tsugutsugu
提出日時 2023-06-17 01:20:03
言語 C++23
(gcc 13.3.0 + boost 1.87.0)
結果
AC  
実行時間 4 ms / 2,000 ms
コード長 3,225 bytes
コンパイル時間 2,886 ms
コンパイル使用メモリ 249,164 KB
実行使用メモリ 6,944 KB
最終ジャッジ日時 2024-06-24 18:11:41
合計ジャッジ時間 4,237 ms
ジャッジサーバーID
（参考情報） 		judge3 / judge1
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
sample AC * 3
other AC * 21
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 #
プレゼンテーションモードにする

#include <bits/stdc++.h>
using namespace std;
#ifdef LOCAL
#include "debug.hpp"
#else
#define debug(...) 1
#endif
template <int m>
struct modint {
    unsigned int v = 0;
    static constexpr int mod() { return m; }
    static constexpr unsigned int umod() { return m; }
    unsigned int val() { return v; }
    modint() : v(0) {}
    modint(long long _v) {
        long long x = (long long)(_v % umod());
        if (x < 0) {
            x += umod();
        }
        v = (unsigned int) x;
    }
    modint operator+() const { return *this; }
    modint operator-() const { return modint() - *this; }
    modint(const modint &rhs) { v = rhs.v; }
    modint &operator+=(const modint &rhs) {
        v += rhs.v;
        if (v >= umod()) {
            v -= umod();
        }
        return *this;
    }
    modint operator+(const modint &rhs) const {
        return modint(*this) += rhs;
    }
    modint &operator-=(const modint &rhs) {
        v -= rhs.v;
        if (v >= umod()) {
            v += umod();
        }
        return *this;
    }
    modint operator-(const modint &rhs) const {
        return modint(*this) -= rhs;
    }
    modint &operator*=(const modint &rhs) {
        unsigned long long x = v;
        x *= rhs.v;
        v = (unsigned int) (x % umod());
        return *this;
    }
    modint operator*(const modint &rhs) const {
        return modint(*this) *= rhs;
    }
    template <typename T>
    modint pow(T n) const {
        modint x = *this, ret = 1;
        while (n) {
            if (n & 1) ret *= x;
            x *= x;
            n >>= 1;
        }
        return ret;
    }
    modint inv() const {
        return pow(umod() - 2);
    }
    modint &operator/=(const modint &rhs) {
        *this *= rhs.inv();
        return *this;
    }
    modint operator/(const modint &rhs) const {
        return modint(*this) /= rhs;
    }
    friend istream &operator>>(istream &is, modint &v) {
        long long x;
        is >> x;
        v.v = x;
        return is;
    }
    friend ostream &operator<<(ostream &os, modint &v) {
        return os << v.v;
    }
};
constexpr int md = 998244353;
// constexpr int md = 1000000007;
vector<modint<md>> fact, inv, inv_fact;
void cominit(int MAX) {
    fact.resize(MAX + 1);
    inv.resize(MAX + 1);
    inv_fact.resize(MAX + 1);
    fact[0] = fact[1] = 1;
    inv_fact[0] = inv_fact[1] = 1;
    inv[1] = 1;
    for (int i = 2; i <= MAX; i++) {
        fact[i] = fact[i - 1] * i;
        inv[i] = -inv[md % i] * (modint<md>) (md / i);
        inv_fact[i] = inv_fact[i - 1] * inv[i];
    }
}
template <typename T>
modint<md> Com(T n, T k) {
    assert(n < (int) fact.size() && k < (int) fact.size());
    if (n < k) return 0;
    if (n < 0 || k < 0) return 0;
    return fact[n] * inv_fact[k] * inv_fact[n - k];
}
template <typename T>
modint<md> Per(T n, T k) {
    assert(n < (int) fact.size() && k < (int) fact.size());
    if (n < k) return 0;
    if (n < 0 || k < 0) return 0;
    return fact[n] * inv_fact[n - k];
}
using Mint = modint<md>;
int main() {
    ios::sync_with_stdio(false);
    cin.tie(nullptr);
    int n, k;
    cin >> n >> k;
    cominit(n);
    Mint ans = Mint(n) * k * (k - 1) / Mint(k).pow(n);
    cout << ans << '\n';
}
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