結果

問題 No.1300 Sum of Inversions
コンテスト
ユーザー siro53
提出日時 2020-11-28 14:21:16
言語 C++17
(gcc 13.3.0 + boost 1.87.0)
結果
AC  
実行時間 156 ms / 2,000 ms
コード長 5,298 bytes
コンパイル時間 2,790 ms
コンパイル使用メモリ 207,400 KB
最終ジャッジ日時 2025-01-16 09:20:18
ジャッジサーバーID
（参考情報） 		judge5 / judge4
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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>
using namespace std;
template <class T> inline bool chmax(T &a, T b) {
    if(a < b) {
        a = b;
        return 1;
    }
    return 0;
}
template <class T> inline bool chmin(T &a, T b) {
    if(a > b) {
        a = b;
        return 1;
    }
    return 0;
}
#define DEBUG
#ifdef DEBUG
template <class T, class U>
ostream &operator<<(ostream &os, const pair<T, U> &p) {
    os << '(' << p.first << ',' << p.second << ')';
    return os;
}
template <class T> ostream &operator<<(ostream &os, const vector<T> &v) {
    os << '{';
    for(int i = 0; i < (int)v.size(); i++) {
        if(i) { os << ','; }
        os << v[i];
    }
    os << '}';
    return os;
}
void debugg() { cerr << endl; }
template <class T, class... Args>
void debugg(const T &x, const Args &... args) {
    cerr << " " << x;
    debugg(args...);
}
#define debug(...)                                                             \
    cerr << __LINE__ << " [" << #__VA_ARGS__ << "]: ", debugg(__VA_ARGS__)
#define dump(x) cerr << __LINE__ << " " << #x << " = " << (x) << endl
#else
#define debug(...) (void(0))
#define dump(x) (void(0))
#endif

struct Setup {
    Setup() {
        cin.tie(0);
        ios::sync_with_stdio(false);
        cout << fixed << setprecision(15);
    }
} __Setup;

using ll = long long;
#define ALL(v) (v).begin(), (v).end()
#define RALL(v) (v).rbegin(), (v).rend()
#define repl(i, a, b) for(int i = a; i < int(b); i++)
#define rep(i, n) repl(i, 0, n)
const int INF = 1 << 30;
const ll LLINF = 1LL << 60;
constexpr int MOD = 998244353;
const int dx[4] = {1, 0, -1, 0};
const int dy[4] = {0, 1, 0, -1};

//-------------------------------------

template <int mod> struct ModInt {
    int x;
    ModInt() : x(0) {}
    ModInt(int64_t y) : x(y >= 0 ? y % mod : (mod - (-y) % mod) % mod) {}
    ModInt &operator+=(const ModInt &p) {
        if((x += p.x) >= mod) x -= mod;
        return *this;
    }
    ModInt &operator-=(const ModInt &p) {
        if((x += mod - p.x) >= mod) x -= mod;
        return *this;
    }
    ModInt &operator*=(const ModInt &p) {
        x = (int)(1LL * x * p.x % mod);
        return *this;
    }
    ModInt &operator/=(const ModInt &p) {
        *this *= p.inverse();
        return *this;
    }
    ModInt operator-() const { return ModInt(-x); }
    ModInt operator+(const ModInt &p) const { return ModInt(*this) += p; }
    ModInt operator-(const ModInt &p) const { return ModInt(*this) -= p; }
    ModInt operator*(const ModInt &p) const { return ModInt(*this) *= p; }
    ModInt operator/(const ModInt &p) const { return ModInt(*this) /= p; }
    ModInt inverse() const {
        int a = x, b = mod, u = 1, v = 0, t;
        while(b > 0) {
            t = a / b;
            swap(a -= t * b, b);
            swap(u -= t * v, v);
        }
        return ModInt(u);
    }
    ModInt pow(int64_t n) const {
        ModInt ret(1), mul(x);
        while(n > 0) {
            if(n & 1) ret *= mul;
            mul *= mul;
            n >>= 1;
        }
        return ret;
    }
    friend ostream &operator<<(ostream &os, const ModInt &p) {
        return os << p.x;
    }
    friend istream &operator>>(istream &is, ModInt &a) {
        int64_t t;
        is >> t;
        a = ModInt<mod>(t);
        return (is);
    }
    static int get_mod() { return mod; }
};

template <typename T> struct BIT {
    vector<T> v;
    BIT(int n) { v.assign(n + 1, 0); }
    // [0, k]
    T sum(int k) {
        T res = 0;
        for(++k; k > 0; k -= k & -k) { res += v[k]; }
        return res;
    }
    // [l, r)
    T sum(int l, int r) {
        return (l == 0 ? sum(r - 1) : sum(r - 1) - sum(l - 1));
    }
    void add(int k, T x) {
        for(++k; k < v.size(); k += k & -k) { v[k] += x; }
    }
};

template <typename T> struct Compress {
    vector<T> v;
    Compress() {}
    Compress(vector<T> vv) : v(vv) {
        sort(ALL(v));
        v.erase(unique(ALL(v)), end(v));
    }
    void build(vector<T> vv) {
        v = vv;
        sort(ALL(v));
        v.erase(unique(ALL(v)), end(v));
    }
    int get(T x) { return (int)(lower_bound(ALL(v), x) - v.begin()); }
    T &operator[](int i) { return v[i]; }
    size_t size() { return v.size(); }
};

using mint = ModInt<MOD>;

int main() {
    int n;
    cin >> n;
    vector<int> a(n);
    rep(i, n) cin >> a[i];
    Compress comp(a);
    int sz = (int)comp.size();

    vector<mint> Lsum(n, 0), Rsum(n, 0);
    vector<int> Lcnt(n, 0), Rcnt(n, 0);

    {
        BIT<mint> val_bit(sz);
        BIT<int> cnt_bit(sz);
        rep(i, n) {
            int id = comp.get(a[i]);
            val_bit.add(id, a[i]);
            cnt_bit.add(id, 1);
            Lsum[i] = val_bit.sum(id + 1, sz);
            Lcnt[i] = cnt_bit.sum(id + 1, sz);
        }
    }
    {
        BIT<mint> val_bit(sz);
        BIT<int> cnt_bit(sz);
        for(int i = n - 1; i >= 0; i--) {
            int id = comp.get(a[i]);
            val_bit.add(id, a[i]);
            cnt_bit.add(id, 1);
            Rsum[i] = val_bit.sum(0, id);
            Rcnt[i] = cnt_bit.sum(0, id);
        }
    }

    mint ans = 0;
    rep(j, n) {
        if(Lcnt[j] == 0 || Rcnt[j] == 0) continue;
        ans += mint(a[j]) * Lcnt[j] * Rcnt[j];
        ans += Lsum[j] * Rcnt[j];
        ans += Rsum[j] * Lcnt[j];
    }
    cout << ans << endl;
}
0