#794955 (C++14) No.2068 Restricted Permutation

• 問題: No.2068 Restricted Permutation
• ユーザー: square1001
• 提出日時: 2022-09-02 22:44:51
• 言語: C++14 (gcc 13.3.0 + boost 1.87.0)
• 結果: AC
• 実行時間: 58 ms / 2,000 ms
• コード長: 1,927 bytes
• コンパイル時間: 1,053 ms
• コンパイル使用メモリ: 71,720 KB
• 実行使用メモリ: 6,820 KB
• 最終ジャッジ日時: 2024-11-16 05:06:24
• 合計ジャッジ時間: 1,919 ms
• ジャッジサーバーID （参考情報）: judge1 / judge4

ファイルパターン	結果
sample	AC * 3
other	AC * 23

ソースコード

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#ifndef CLASS_MODINT
#define CLASS_MODINT
#include <cstdint>
template <std::uint32_t mod>
class modint {
private:
    std::uint32_t n;
public:
    modint() : n(0) {};
    modint(std::int64_t n_) : n((n_ >= 0 ? n_ : mod - (-n_) % mod) % mod) {};
    static constexpr std::uint32_t get_mod() { return mod; }
    std::uint32_t get() const { return n; }
    bool operator==(const modint& m) const { return n == m.n; }
    bool operator!=(const modint& m) const { return n != m.n; }
    modint& operator+=(const modint& m) { n += m.n; n = (n < mod ? n : n - mod); return *this; }
    modint& operator-=(const modint& m) { n += mod - m.n; n = (n < mod ? n : n - mod); return *this; }
    modint& operator*=(const modint& m) { n = std::uint64_t(n) * m.n % mod; return *this; }
    modint operator+(const modint& m) const { return modint(*this) += m; }
    modint operator-(const modint& m) const { return modint(*this) -= m; }
    modint operator*(const modint& m) const { return modint(*this) *= m; }
    modint inv() const { return (*this).pow(mod - 2); }
    modint pow(std::uint64_t b) const {
        modint ans = 1, m = modint(*this);
        while (b) {
            if (b & 1) ans *= m;
            m *= m;
            b >>= 1;
        }
        return ans;
    }
};
#endif // CLASS_MODINT
#include <vector>
#include <iostream>
using namespace std;
using mint = modint<998244353>;
int main() {
    // step #1. read input
    int N, K, X;
    cin >> N >> K >> X;
    K -= 1;
    X -= 1;
    // step #2. preparation
    vector<mint> fact(N + 1);
    fact[0] = 1;
    for (int i = 1; i <= N; i++) {
        fact[i] = fact[i - 1] * i;
    }
    // step #3. calculation
    mint answer = 0;
    for (int i = 0; i < N; i++) {
        if (i < K) {
            answer += fact[N - i - 1] * (mint(N - i - 2) * mint(2).inv() + mint(N - X - 1) * mint(N - 1).inv());
        }
        if (i > K) {
            answer += fact[N - i - 1] * (N - i - 1) * mint(2).inv();
        }
    }
    answer += fact[N - K - 1] * (N - K - 1) * mint(X) * mint(N - 1).inv();
    answer *= fact[N - 1];
    cout << answer.get() << endl;
    return 0;
}
 
 
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