結果

問題 No.1300 Sum of Inversions
コンテスト
ユーザー scol_kp
提出日時 2020-11-28 00:14:42
言語 C++17
(gcc 13.3.0 + boost 1.87.0)
結果
AC  
実行時間 178 ms / 2,000 ms
コード長 8,685 bytes
コンパイル時間 2,329 ms
コンパイル使用メモリ 206,680 KB
最終ジャッジ日時 2025-01-16 08:49:54
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
sample AC * 3
other AC * 34
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 # 

#include <bits/stdc++.h>
#define FASTIO
using namespace std;

using ll = long long;
using Vi = std::vector<int>;
using Vl = std::vector<ll>;
using Pii = std::pair<int, int>;
using Pll = std::pair<ll, ll>;

constexpr int I_INF = std::numeric_limits<int>::max();
constexpr ll L_INF = std::numeric_limits<ll>::max();

template <typename T1, typename T2>
inline bool chmin(T1& a, const T2& b) {
    if (a > b) {
        a = b;
        return true;
    }
    return false;
}
template <typename T1, typename T2>
inline bool chmax(T1& a, const T2& b) {
    if (a < b) {
        a = b;
        return true;
    }
    return false;
}

template <ostream& os = std::cout>
class Prints {
private:
    class __Prints {
    public:
        __Prints(const char* sep, const char* term) : sep(sep), term(term) {}
        template <class... Args>
        auto operator()(const Args&... args) const -> decltype((os << ... << std::declval<Args>()), void()) { print(args...); }
        template <typename T>
        auto pvec(const T& vec, size_t sz) const -> decltype(os << std::declval<decltype(std::declval<T>()[0])>(), void()) {
            for (size_t i = 0; i < sz; i++)
                os << vec[i] << (i == sz - 1 ? term : sep);
        }
        template <typename T>
        auto pmat(const T& mat, size_t h, size_t w) -> decltype(os << std::declval<decltype(std::declval<T>()[0][0])>(), void()) {
            for (size_t i = 0; i < h; i++)
                for (size_t j = 0; j < w; j++)
                    os << mat[i][j] << (j == w - 1 ? term : sep);
        }

    private:
        const char *sep, *term;
        void print() const { os << term; }
        void print_rest() const { os << term; }
        template <class T, class... Tail>
        void print(const T& head, const Tail&... tail) const { os << head, print_rest(tail...); }
        template <class T, class... Tail>
        void print_rest(const T& head, const Tail&... tail) const { os << sep << head, print_rest(tail...); }
    };

public:
    Prints() {}
    __Prints operator()(const char* sep = " ", const char* term = "\n") const { return __Prints(sep, term); }
};

Prints<> prints;
Prints<std::cerr> prints_err;

//%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%

template <std::int_fast64_t Modulus>
class ModInt {
    using i64 = std::int_fast64_t;

private:
    i64 m_value;

public:
    constexpr ModInt(const i64 x = 0) noexcept : m_value(x) {
        if (m_value < -Modulus || m_value >= Modulus) m_value %= Modulus;
        if (m_value < 0) m_value += Modulus;
    }

    constexpr i64 const& value() const noexcept { return m_value; }

    constexpr ModInt& operator+=(const ModInt rhs) noexcept {
        m_value += rhs.m_value;
        if (m_value >= Modulus) {
            m_value -= Modulus;
        }
        return *this;
    }
    constexpr ModInt& operator-=(const ModInt rhs) noexcept {
        if (m_value < rhs.m_value) {
            m_value += Modulus;
        }
        m_value -= rhs.m_value;
        return *this;
    }
    constexpr ModInt& operator*=(const ModInt rhs) noexcept {
        m_value *= rhs.m_value;
        if (m_value >= Modulus) m_value %= Modulus;
        return *this;
    }
    constexpr ModInt& operator/=(ModInt rhs) noexcept {
        *this *= rhs.inv();
        return *this;
    }

    constexpr ModInt& operator++() noexcept {
        *this += 1;
        return *this;
    }
    constexpr ModInt operator++(int) noexcept {
        ModInt res = *this;
        *this += 1;
        return res;
    }
    constexpr ModInt& operator--() noexcept {
        *this -= 1;
        return *this;
    }
    constexpr ModInt operator--(int) noexcept {
        ModInt res = *this;
        *this -= 1;
        return res;
    }

    constexpr ModInt inv() const noexcept {
        i64 q = m_value;
        i64 b = Modulus, u = 1, v = 0;
        i64 tmp = 0;
        while (b) {
            i64 t = q / b;
            q -= t * b;
            tmp = q, q = b, b = tmp;
            u -= t * v;
            tmp = u, u = v, v = tmp;
        }
        if (u < -Modulus || u >= Modulus) u %= Modulus;
        if (u < 0) u += Modulus;
        return u;
    }

    constexpr ModInt pow(i64 k) const noexcept {
        ModInt res = 1;
        ModInt tmp = 0;
        if (k < 0) {
            tmp = this->inv();
            k = -k;
        }
        else {
            tmp = *this;
        }
        for (; k > 0; k >>= 1) {
            if (k & 1) res *= tmp;
            tmp *= tmp;
        }
        return res;
    }

    friend constexpr ModInt operator+(const ModInt& a) noexcept {
        return a;
    }
    friend constexpr ModInt operator-(const ModInt& a) noexcept {
        return ModInt(0) - a;
    }
    friend constexpr ModInt operator+(const ModInt& lhs, const ModInt& rhs) noexcept {
        return ModInt<Modulus>(lhs) += rhs;
    }
    friend constexpr ModInt operator-(const ModInt& lhs, const ModInt& rhs) noexcept {
        return ModInt<Modulus>(lhs) -= rhs;
    }
    friend constexpr ModInt operator*(const ModInt& lhs, const ModInt& rhs) noexcept {
        return ModInt<Modulus>(lhs) *= rhs;
    }
    friend constexpr ModInt operator/(const ModInt& lhs, const ModInt& rhs) noexcept {
        return ModInt<Modulus>(lhs) /= rhs;
    }

    friend constexpr bool operator<(const ModInt& lhs, const ModInt& rhs) noexcept {
        return lhs.m_value < rhs.m_value;
    }
    friend constexpr bool operator>(const ModInt& lhs, const ModInt& rhs) noexcept {
        return lhs.m_value > rhs.m_value;
    }
    friend constexpr bool operator<=(const ModInt& lhs, const ModInt& rhs) noexcept {
        return lhs.m_value <= rhs.m_value;
    }
    friend constexpr bool operator>=(const ModInt& lhs, const ModInt& rhs) noexcept {
        return lhs.m_value >= rhs.m_value;
    }

    friend constexpr bool operator==(const ModInt& lhs, const ModInt& rhs) noexcept {
        return lhs.m_value == rhs.m_value;
    }
    friend constexpr bool operator!=(const ModInt& lhs, const ModInt& rhs) noexcept {
        return lhs.m_value != rhs.m_value;
    }

    friend std::istream& operator>>(std::istream& is, ModInt& rhs) {
        i64 a;
        is >> a;
        rhs = a;
        return is;
    }
    friend std::ostream& operator<<(std::ostream& os, const ModInt& rhs) {
        os << rhs.m_value;
        return os;
    }
};

constexpr long long MOD = 998244353;
using Mint = ModInt<MOD>;

template <typename T>
class BIT {
private:
    int n;
    std::vector<T> vec;

public:
    BIT(int n) : n(n), vec(n + 1) {}
    void add(int i, const T& a) {
        for (++i; i <= n; i += i & (-i)) {
            vec[i] += a;
        }
    }
    T query(int i) const {
        T res = 0;
        for (; i >= 1; i -= i & (-i)) {
            res += vec[i];
        }
        return res;
    }
    T query(int i, int j) const {
        return query(j) - query(i);
    }
    size_t size() const noexcept {
        return n;
    }
    void reset() noexcept {
        std::fill(vec.begin(), vec.end(), static_cast<T>(0));
    }
};

void solve() {
    int N;
    cin >> N;
    Vl A(N);
    for (ll i = 0; i < N; i++) {
        cin >> A[i];
    }
    Vl cc = A;
    sort(cc.begin(), cc.end());
    cc.erase(unique(cc.begin(), cc.end()), cc.end());
    int sz = (int)cc.size();
    BIT<Mint> fwt1(sz), fwt2(sz);
    vector<Mint> sums_l(N), sums_r(N);
    vector<Mint> cnts_l(N), cnts_r(N);
    for (ll i = 0; i < N; i++) {
        int idx = lower_bound(cc.begin(), cc.end(), A[i]) - cc.begin();
        sums_l[i] = fwt1.query(idx + 1, sz);
        cnts_l[i] = fwt2.query(idx + 1, sz);
        fwt1.add(idx, A[i]);
        fwt2.add(idx, 1);
    }
    fwt1.reset(), fwt2.reset();
    for (ll i = N - 1; i >= 0; i--) {
        int idx = lower_bound(cc.begin(), cc.end(), A[i]) - cc.begin();
        sums_r[i] = fwt1.query(0, idx);
        cnts_r[i] = fwt2.query(0, idx);
        fwt1.add(idx, A[i]);
        fwt2.add(idx, 1);
    }
    Mint ans = 0;
    for (ll i = 0; i < N; i++) {
        if (cnts_l[i] > 0 && cnts_r[i] > 0) {
            ans += sums_l[i] * cnts_r[i] + sums_r[i] * cnts_l[i] + A[i] * cnts_l[i] * cnts_r[i];
        }
    }
    prints()(ans);
}

//%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%

int main() {
#ifdef FASTIO
    std::cin.tie(nullptr), std::cout.tie(nullptr);
    std::ios::sync_with_stdio(false);
#endif
#ifdef FILEINPUT
    std::ifstream ifs("./in_out/input.txt");
    std::cin.rdbuf(ifs.rdbuf());
#endif
#ifdef FILEOUTPUT
    std::ofstream ofs("./in_out/output.txt");
    std::cout.rdbuf(ofs.rdbuf());
#endif
    std::cout << std::setprecision(18) << std::fixed;
    solve();
    std::cout << std::flush;
    return 0;
}
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