#1026233 (C++23) No.2616 中央番目の中央値

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問題	No.2616 中央番目の中央値
コンテスト
ユーザー	vjudge1
提出日時	2024-11-12 00:54:37
言語	C++23 (gcc 13.3.0 + boost 1.87.0)
結果	AC
実行時間	58 ms / 2,000 ms
コード長	16,545 bytes
コンパイル時間	3,965 ms
コンパイル使用メモリ	266,280 KB
実行使用メモリ	10,240 KB
最終ジャッジ日時	2024-11-12 00:54:45
合計ジャッジ時間	7,288 ms
ジャッジサーバーID （参考情報）	judge1 / judge4
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ファイルパターン	結果
other	AC * 37
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ソースコード

raw source code
#pragma GCC optimize("O3,unroll-loops")
// #pragma GCC target("avx,popcnt,sse4,abm")
#include<bits/stdc++.h>
using namespace std;
#define ZTMYACANESOCUTE ios_base::sync_with_stdio(0), cin.tie(0)
#define ll long long
#define ull unsigned long long
#define pb push_back
#define all(a) (a).begin(), (a).end()
#define debug(x) cerr << #x << " = " << x << '\n';
#define rep(X, a, b) for(int X = a; X < b; ++X)
#define pii pair<int, int>
#define pll pair<ll, ll>
#define pld pair<ld, ld>
#define ld long double
#define F first
#define S second

pii operator + (const pii &p1, const pii &p2) { return make_pair(p1.F + p2.F, p1.S + p2.S); }
pii operator - (const pii &p1, const pii &p2) { return make_pair(p1.F - p2.F, p1.S - p2.S); }
pll operator + (const pll &p1, const pll &p2) { return make_pair(p1.F + p2.F, p1.S + p2.S); }
pll operator - (const pll &p1, const pll &p2) { return make_pair(p1.F - p2.F, p1.S - p2.S); }

template<class T> bool chmin(T &a, T b) { return (b < a && (a = b, true)); }
template<class T> bool chmax(T &a, T b) { return (a < b && (a = b, true)); }

#define lpos pos << 1
#define rpos pos << 1 | 1
 
template<typename A, typename B> ostream& operator<<(ostream &os, const pair<A, B> &p) { return os << '(' << p.first << "," << p.second << ')'; }
template<typename A> ostream& operator << (ostream &os, const vector<A> &p) { for(const auto &a : p) os << a << " "; os << '\n'; return os; }
 
const int MAXN = 2e5 + 5, MOD = 998244353, IINF = 1e9 + 7, MOD2 = 1000000007;
const double eps = 1e-9;
const ll LINF = 1e18L + 5;
const int B = 320;

// mt19937 rng(chrono::steady_clock::now().time_since_epoch().count());
// int get_rand(int l, int r){ return uniform_int_distribution<int>(l, r)(rng); }
 
ll fpow(ll x, ll exp, ll mod = LLONG_MAX){ ll res = 1; while(exp){ if(exp & 1) res = res * x % mod; x = x * x % mod; exp >>= 1;} return res; }

#ifdef _MSC_VER
#include <intrin.h>
#endif

namespace atcoder_modint {

namespace internal {

#ifndef _MSC_VER
template <class T>
using is_signed_int128 =
    typename conditional<is_same<T, __int128_t>::value ||
                                  is_same<T, __int128>::value,
                              true_type,
                              false_type>::type;

template <class T>
using is_unsigned_int128 =
    typename conditional<is_same<T, __uint128_t>::value ||
                                  is_same<T, unsigned __int128>::value,
                              true_type,
                              false_type>::type;

template <class T>
using make_unsigned_int128 =
    typename std::conditional<is_same<T, __int128_t>::value,
                              __uint128_t,
                              unsigned __int128>;

template <class T>
using is_integral = typename conditional<is_integral<T>::value ||
                                                  is_signed_int128<T>::value ||
                                                  is_unsigned_int128<T>::value,
                                              true_type,
                                              false_type>::type;

template <class T>
using is_signed_int = typename conditional<(is_integral<T>::value &&
                                                 is_signed<T>::value) ||
                                                    is_signed_int128<T>::value,
                                                true_type,
                                                false_type>::type;

template <class T>
using is_unsigned_int =
    typename conditional<(is_integral<T>::value &&
                               is_unsigned<T>::value) ||
                                  is_unsigned_int128<T>::value,
                              true_type,
                              false_type>::type;

template <class T>
using to_unsigned = typename conditional<
    is_signed_int128<T>::value,
    make_unsigned_int128<T>,
    typename conditional<is_signed<T>::value,
                              make_unsigned<T>,
                              common_type<T>>::type>::type;

#else

template <class T> using is_integral = typename is_integral<T>;

template <class T>
using is_signed_int =
    typename conditional<is_integral<T>::value && is_signed<T>::value,
                              true_type,
                              false_type>::type;

template <class T>
using is_unsigned_int =
    typename conditional<is_integral<T>::value &&
                                  is_unsigned<T>::value,
                              true_type,
                              false_type>::type;

template <class T>
using to_unsigned = typename conditional<is_signed_int<T>::value,
                                              make_unsigned<T>,
                                              common_type<T>>::type;

#endif

template <class T>
using is_signed_int_t = enable_if_t<is_signed_int<T>::value>;

template <class T>
using is_unsigned_int_t = enable_if_t<is_unsigned_int<T>::value>;

template <class T> using to_unsigned_t = typename to_unsigned<T>::type;

// @param m `1 <= m`
// @return x mod m
constexpr long long safe_mod(long long x, long long m) {
    x %= m;
    if (x < 0) x += m;
    return x;
}

constexpr long long pow_mod_constexpr(long long x, long long n, int m) {
    if (m == 1) return 0;
    unsigned int _m = (unsigned int)(m);
    unsigned long long r = 1;
    unsigned long long y = safe_mod(x, m);
    while (n) {
        if (n & 1) r = (r * y) % _m;
        y = (y * y) % _m;
        n >>= 1;
    }
    return r;
}

// Reference:
// M. Forisek and J. Jancina,
// Fast Primality Testing for Integers That Fit into a Machine Word
// @param n `0 <= n`
constexpr bool is_prime_constexpr(int n) {
    if (n <= 1) return false;
    if (n == 2 || n == 7 || n == 61) return true;
    if (n % 2 == 0) return false;
    long long d = n - 1;
    while (d % 2 == 0) d /= 2;
    constexpr long long bases[3] = {2, 7, 61};
    for (long long a : bases) {
        long long t = d;
        long long y = pow_mod_constexpr(a, t, n);
        while (t != n - 1 && y != 1 && y != n - 1) {
            y = y * y % n;
            t <<= 1;
        }
        if (y != n - 1 && t % 2 == 0) {
            return false;
        }
    }
    return true;
}
template <int n> constexpr bool is_prime = is_prime_constexpr(n);

// @param b `1 <= b`
// @return pair(g, x) s.t. g = gcd(a, b), xa = g (mod b), 0 <= x < b/g
constexpr pair<long long, long long> inv_gcd(long long a, long long b) {
    a = safe_mod(a, b);
    if (a == 0) return {b, 0};

    // Contracts:
    // [1] s - m0 * a = 0 (mod b)
    // [2] t - m1 * a = 0 (mod b)
    // [3] s * |m1| + t * |m0| <= b
    long long s = b, t = a;
    long long m0 = 0, m1 = 1;

    while (t) {
        long long u = s / t;
        s -= t * u;
        m0 -= m1 * u;  // |m1 * u| <= |m1| * s <= b

        // [3]:
        // (s - t * u) * |m1| + t * |m0 - m1 * u|
        // <= s * |m1| - t * u * |m1| + t * (|m0| + |m1| * u)
        // = s * |m1| + t * |m0| <= b

        auto tmp = s;
        s = t;
        t = tmp;
        tmp = m0;
        m0 = m1;
        m1 = tmp;
    }
    // by [3]: |m0| <= b/g
    // by g != b: |m0| < b/g
    if (m0 < 0) m0 += b / s;
    return {s, m0};
}

// Fast modular multiplication by barrett reduction
// Reference: https://en.wikipedia.org/wiki/Barrett_reduction
// NOTE: reconsider after Ice Lake
struct barrett {
    unsigned int _m;
    unsigned long long im;

    // @param m `1 <= m < 2^31`
    explicit barrett(unsigned int m) : _m(m), im((unsigned long long)(-1) / m + 1) {}

    // @return m
    unsigned int umod() const { return _m; }

    // @param a `0 <= a < m`
    // @param b `0 <= b < m`
    // @return `a * b % m`
    unsigned int mul(unsigned int a, unsigned int b) const {
        // [1] m = 1
        // a = b = im = 0, so okay

        // [2] m >= 2
        // im = ceil(2^64 / m)
        // -> im * m = 2^64 + r (0 <= r < m)
        // let z = a*b = c*m + d (0 <= c, d < m)
        // a*b * im = (c*m + d) * im = c*(im*m) + d*im = c*2^64 + c*r + d*im
        // c*r + d*im < m * m + m * im < m * m + 2^64 + m <= 2^64 + m * (m + 1) < 2^64 * 2
        // ((ab * im) >> 64) == c or c + 1
        unsigned long long z = a;
        z *= b;
#ifdef _MSC_VER
        unsigned long long x;
        _umul128(z, im, &x);
#else
        unsigned long long x =
            (unsigned long long)(((unsigned __int128)(z)*im) >> 64);
#endif
        unsigned int v = (unsigned int)(z - x * _m);
        if (_m <= v) v += _m;
        return v;
    }
};

struct modint_base {};
struct static_modint_base : modint_base {};

template <class T> using is_modint = is_base_of<modint_base, T>;
template <class T> using is_modint_t = enable_if_t<is_modint<T>::value>;

}  // namespace internal

template <int m, enable_if_t<(1 <= m)>* = nullptr>
struct static_modint : internal::static_modint_base {
    using mint = static_modint;

  public:
    static constexpr int mod() { return m; }
    static mint raw(int v) {
        mint x;
        x._v = v;
        return x;
    }

    static_modint() : _v(0) {}
    template <class T, internal::is_signed_int_t<T>* = nullptr>
    static_modint(T v) {
        long long x = (long long)(v % (long long)(umod()));
        if (x < 0) x += umod();
        _v = (unsigned int)(x);
    }
    template <class T, internal::is_unsigned_int_t<T>* = nullptr>
    static_modint(T v) {
        _v = (unsigned int)(v % umod());
    }

    unsigned int val() const { return _v; }

    mint& operator++() {
        _v++;
        if (_v == umod()) _v = 0;
        return *this;
    }
    mint& operator--() {
        if (_v == 0) _v = umod();
        _v--;
        return *this;
    }
    mint operator++(int) {
        mint result = *this;
        ++*this;
        return result;
    }
    mint operator--(int) {
        mint result = *this;
        --*this;
        return result;
    }

    mint& operator+=(const mint& rhs) {
        _v += rhs._v;
        if (_v >= umod()) _v -= umod();
        return *this;
    }
    mint& operator-=(const mint& rhs) {
        _v -= rhs._v;
        if (_v >= umod()) _v += umod();
        return *this;
    }
    mint& operator*=(const mint& rhs) {
        unsigned long long z = _v;
        z *= rhs._v;
        _v = (unsigned int)(z % umod());
        return *this;
    }
    mint& operator/=(const mint& rhs) { return *this = *this * rhs.inv(); }

    mint operator+() const { return *this; }
    mint operator-() const { return mint() - *this; }

    mint pow(long long n) const {
        assert(0 <= n);
        mint x = *this, r = 1;
        while (n) {
            if (n & 1) r *= x;
            x *= x;
            n >>= 1;
        }
        return r;
    }
    mint inv() const {
        if (prime) {
            assert(_v);
            return pow(umod() - 2);
        } else {
            auto eg = internal::inv_gcd(_v, m);
            assert(eg.first == 1);
            return eg.second;
        }
    }

    friend mint operator+(const mint& lhs, const mint& rhs) {
        return mint(lhs) += rhs;
    }
    friend mint operator-(const mint& lhs, const mint& rhs) {
        return mint(lhs) -= rhs;
    }
    friend mint operator*(const mint& lhs, const mint& rhs) {
        return mint(lhs) *= rhs;
    }
    friend mint operator/(const mint& lhs, const mint& rhs) {
        return mint(lhs) /= rhs;
    }
    friend bool operator==(const mint& lhs, const mint& rhs) {
        return lhs._v == rhs._v;
    }
    friend bool operator!=(const mint& lhs, const mint& rhs) {
        return lhs._v != rhs._v;
    }

  private:
    unsigned int _v;
    static constexpr unsigned int umod() { return m; }
    static constexpr bool prime = internal::is_prime<m>;
};

template <int id> struct dynamic_modint : internal::modint_base {
    using mint = dynamic_modint;

  public:
    static int mod() { return (int)(bt.umod()); }
    static void set_mod(int m) {
        assert(1 <= m);
        bt = internal::barrett(m);
    }
    static mint raw(int v) {
        mint x;
        x._v = v;
        return x;
    }

    dynamic_modint() : _v(0) {}
    template <class T, internal::is_signed_int_t<T>* = nullptr>
    dynamic_modint(T v) {
        long long x = (long long)(v % (long long)(mod()));
        if (x < 0) x += mod();
        _v = (unsigned int)(x);
    }
    template <class T, internal::is_unsigned_int_t<T>* = nullptr>
    dynamic_modint(T v) {
        _v = (unsigned int)(v % mod());
    }

    unsigned int val() const { return _v; }

    mint& operator++() {
        _v++;
        if (_v == umod()) _v = 0;
        return *this;
    }
    mint& operator--() {
        if (_v == 0) _v = umod();
        _v--;
        return *this;
    }
    mint operator++(int) {
        mint result = *this;
        ++*this;
        return result;
    }
    mint operator--(int) {
        mint result = *this;
        --*this;
        return result;
    }

    mint& operator+=(const mint& rhs) {
        _v += rhs._v;
        if (_v >= umod()) _v -= umod();
        return *this;
    }
    mint& operator-=(const mint& rhs) {
        _v += mod() - rhs._v;
        if (_v >= umod()) _v -= umod();
        return *this;
    }
    mint& operator*=(const mint& rhs) {
        _v = bt.mul(_v, rhs._v);
        return *this;
    }
    mint& operator/=(const mint& rhs) { return *this = *this * rhs.inv(); }

    mint operator+() const { return *this; }
    mint operator-() const { return mint() - *this; }

    mint pow(long long n) const {
        assert(0 <= n);
        mint x = *this, r = 1;
        while (n) {
            if (n & 1) r *= x;
            x *= x;
            n >>= 1;
        }
        return r;
    }
    mint inv() const {
        auto eg = internal::inv_gcd(_v, mod());
        assert(eg.first == 1);
        return eg.second;
    }

    friend mint operator+(const mint& lhs, const mint& rhs) {
        return mint(lhs) += rhs;
    }
    friend mint operator-(const mint& lhs, const mint& rhs) {
        return mint(lhs) -= rhs;
    }
    friend mint operator*(const mint& lhs, const mint& rhs) {
        return mint(lhs) *= rhs;
    }
    friend mint operator/(const mint& lhs, const mint& rhs) {
        return mint(lhs) /= rhs;
    }
    friend bool operator==(const mint& lhs, const mint& rhs) {
        return lhs._v == rhs._v;
    }
    friend bool operator!=(const mint& lhs, const mint& rhs) {
        return lhs._v != rhs._v;
    }

  private:
    unsigned int _v;
    static internal::barrett bt;
    static unsigned int umod() { return bt.umod(); }
};
template <int id> internal::barrett dynamic_modint<id>::bt(998244353);

using modint998244353 = static_modint<998244353>;
using modint1000000007 = static_modint<1000000007>;
using modint = dynamic_modint<-1>;

namespace internal {

template <class T>
using is_static_modint = is_base_of<internal::static_modint_base, T>;

template <class T>
using is_static_modint_t = enable_if_t<is_static_modint<T>::value>;

template <class> struct is_dynamic_modint : public false_type {};
template <int id>
struct is_dynamic_modint<dynamic_modint<id>> : public true_type {};

template <class T>
using is_dynamic_modint_t = enable_if_t<is_dynamic_modint<T>::value>;

}  // namespace internal

}  // namespace atcoder_modint

using mint = atcoder_modint::modint998244353;

// need modint
vector<mint> fac, inv;

inline void init (int n) {
    fac.resize(n + 1);
    inv.resize(n + 1);
    fac[0] = inv[0] = 1;
    rep (i, 1, n + 1) fac[i] = fac[i - 1] * i;
    inv[n] = fac[n].inv();
    for (int i = n; i > 0; --i) inv[i - 1] = inv[i] * i;
}

inline mint C(int n, int k) {
    if (k > n || k < 0) return 0;
    return fac[n] * inv[k] * inv[n - k];
}

inline mint H(int n, int m) {
    return C(n + m - 1, m);
}

struct FenwickTree{
    vector<ll> BIT;
    FenwickTree(int n) : BIT(n + 1, 0) {}

    void mod(int x, ll val) {
        while(x < BIT.size()){
            BIT[x] += val;
            x += x & -x;
        }
    }

    ll query(int x) {
        ll res = 0;
        while (x) {
            res += BIT[x];
            x -= x & -x;
        }
        return res;
    }

    ll rquery(int l, int r) {
        return query(r) - query(l - 1);
    }
};

void solve() {
    int n; cin >> n;
    init(2 * n);
    FenwickTree bit(n);
    mint ans = 0;
    rep (i, 0, n) {
        int p; cin >> p;
        int a = bit.query(p), b = i - a, c = p - 1 - a, d = n - 1 - a - b - c;
        ans += C(a + d, a) * C(b + c, b);
        bit.mod(p, 1);
    }
    cout << ans.val() << '\n';
}
 
int main() {
    ZTMYACANESOCUTE;
    int T = 1;
    // cin >> T;
    while (T--) {
        solve();
    }
}
yukicoder

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ソースコード
