#946964 (C++23) No.2616 中央番目の中央値

• 問題: No.2616 中央番目の中央値
• ユーザー: nono00
• 提出日時: 2024-01-27 07:42:53
• 言語: C++23 (gcc 12.3.0 + boost 1.83.0)
• 結果: AC
• 実行時間: 62 ms / 2,000 ms
• コード長: 4,536 bytes
• コンパイル時間: 3,418 ms
• コンパイル使用メモリ: 250,312 KB
• 実行使用メモリ: 10,328 KB
• 最終ジャッジ日時: 2024-09-28 09:34:48
• 合計ジャッジ時間: 5,213 ms
• ジャッジサーバーID （参考情報）: judge1 / judge5

入力	結果	実行時間; 実行使用メモリ
testcase_00	AC	7 ms; 7,984 KB
testcase_01	AC	6 ms; 8,020 KB
testcase_02	AC	6 ms; 8,004 KB
testcase_03	AC	6 ms; 8,092 KB
testcase_04	AC	6 ms; 8,152 KB
testcase_05	AC	6 ms; 7,992 KB
testcase_06	AC	6 ms; 8,020 KB
testcase_07	AC	5 ms; 8,120 KB
testcase_08	AC	7 ms; 8,196 KB
testcase_09	AC	7 ms; 8,108 KB
testcase_10	AC	7 ms; 8,136 KB
testcase_11	AC	6 ms; 7,988 KB
testcase_12	AC	7 ms; 8,076 KB
testcase_13	AC	6 ms; 8,048 KB
testcase_14	AC	6 ms; 8,140 KB
testcase_15	AC	9 ms; 8,140 KB
testcase_16	AC	10 ms; 8,248 KB
testcase_17	AC	10 ms; 8,232 KB
testcase_18	AC	14 ms; 8,172 KB
testcase_19	AC	23 ms; 8,740 KB
testcase_20	AC	22 ms; 8,544 KB
testcase_21	AC	39 ms; 9,436 KB
testcase_22	AC	55 ms; 10,252 KB
testcase_23	AC	59 ms; 10,224 KB
testcase_24	AC	46 ms; 10,236 KB
testcase_25	AC	46 ms; 10,240 KB
testcase_26	AC	56 ms; 10,228 KB
testcase_27	AC	60 ms; 10,328 KB
testcase_28	AC	57 ms; 10,072 KB
testcase_29	AC	55 ms; 10,256 KB
testcase_30	AC	58 ms; 10,244 KB
testcase_31	AC	57 ms; 10,200 KB
testcase_32	AC	59 ms; 10,272 KB
testcase_33	AC	60 ms; 10,152 KB
testcase_34	AC	62 ms; 10,216 KB
testcase_35	AC	60 ms; 10,072 KB
testcase_36	AC	54 ms; 10,264 KB

ソースコード

#include <bits/stdc++.h>

#include <vector>

namespace nono {

template <class T>
class FenwickTree {
  public:
    FenwickTree(int size = 0): size_(size), data_(size_ + 1) {}

    void add(int i, const T& v) {
        for (++i; i <= size_; i += i & -i) {
            data_[i] += v;
        }
    }

    T sum(int i) const {
        T result{};
        for (; i > 0; i -= i & -i) {
            result += data_[i];
        }
        return result;
    }

    T sum(int l, int r) const {
        return sum(r) - sum(l);
    }

  private:
    int size_;
    std::vector<T> data_;
};

}  //  namespace nono
#include <iostream>

namespace nono {

namespace internal {

constexpr bool is_prime(unsigned long long n) {
    for (unsigned long long i = 2; i * i <= n; i++) {
        if (n % i == 0) return false;
    }
    return true;
}

}  //  namespace internal

template <unsigned long long MOD = 998244353>
class Modint {
  public:
    static_assert(internal::is_prime(MOD));

    constexpr Modint(unsigned long long value = 0): value_(value % MOD) {}

    constexpr Modint pow(long long exp) const {
        Modint result(1);
        Modint base(*this);
        while (exp > 0) {
            if (exp & 1) {
                result *= base;
            }
            base *= base;
            exp >>= 1;
        }
        return result;
    }

    constexpr Modint inv() const {
        return pow(MOD - 2);
    }

    void set(unsigned long long value) {
        if (value >= MOD) value %= MOD;
        value_ = value;
    }

    unsigned long long get() const {
        return value_;
    }

    friend constexpr bool operator==(const Modint lhs, const Modint rhs) {
        return lhs.value_ == rhs.value_;
    }

    constexpr Modint& operator+=(const Modint other) {
        this->value_ += other.value_;
        if (this->value_ >= MOD) this->value_ -= MOD;
        return *this;
    }

    constexpr Modint& operator-=(const Modint other) {
        this->value_ += MOD - other.value_;
        if (this->value_ >= MOD) this->value_ -= MOD;
        return *this;
    }

    constexpr Modint& operator*=(const Modint other) {
        this->value_ *= other.value_;
        if (this->value_ >= MOD) this->value_ %= MOD;
        return *this;
    }

    constexpr Modint& operator/=(const Modint other) {
        return *this *= other.inv();
    }

    constexpr friend Modint operator+(const Modint lhs, const Modint rhs) {
        return Modint(lhs) += rhs;
    }
    constexpr friend Modint operator-(const Modint lhs, const Modint rhs) {
        return Modint(lhs) -= rhs;
    }
    constexpr friend Modint operator*(const Modint lhs, const Modint rhs) {
        return Modint(lhs) *= rhs;
    }
    constexpr friend Modint operator/(const Modint lhs, const Modint rhs) {
        return Modint(lhs) /= rhs;
    }

    friend std::istream& operator>>(std::istream& stream, Modint& mint) {
        unsigned long long value;
        stream >> value;
        mint.set(value);
        return stream;
    }

    friend std::ostream& operator<<(std::ostream& stream, Modint mint) {
        stream << mint.get();
        return stream;
    }

  private:
    unsigned long long value_;
};

using Modint998244353 = Modint<998244353>;
using Modint1000000007 = Modint<1000000007>;

}  //  namespace nono

void solve() {
    using Mint = nono::Modint998244353;
    constexpr int N = 300005;
    std::array<Mint, N> fact, fact_inv;
    fact.fill(1);
    fact_inv.fill(1);
    for (int i = 1; i < N; i++) fact[i] = fact[i - 1] * i;
    fact_inv[N - 1] = fact[N - 1].inv();
    for (int i = N - 1; i > 0; i--) fact_inv[i - 1] = fact_inv[i] * i;
    auto binom = [&](int n, int k) {
        return fact.at(n) * fact_inv.at(k) * fact_inv.at(n - k);
    };

    int n;
    std::cin >> n;
    std::vector<int> p(n);
    for (int i = 0; i < n; i++) std::cin >> p[i];
    for (int i = 0; i < n; i++) p[i]--;
    nono::FenwickTree<int> fenwick(n);
    Mint ans = 0;
    for (int i = 0; i < n; i++) {
        int small_left = fenwick.sum(0, p[i]);
        int big_left = i - small_left;
        int small_right = p[i] - small_left;
        int big_right = (n - p[i] - 1) - big_left;
        Mint left = binom(small_left + big_right, small_left);
        Mint right = binom(small_right + big_left, small_right);
        ans += left * right;
        fenwick.add(p[i], 1);
    }
    std::cout << ans << '\n';
}

int main() {
    std::cin.tie(0)->sync_with_stdio(0);
    std::cout << std::fixed << std::setprecision(16);
    int t = 1;

    while (t--) solve();
}