結果

問題 No.1300 Sum of Inversions
ユーザー bond_cmprogbond_cmprog
提出日時 2020-11-27 22:52:10
言語 C++17
(gcc 13.3.0 + boost 1.87.0)
結果
AC  
実行時間 471 ms / 2,000 ms
コード長 11,292 bytes
コンパイル時間 3,032 ms
コンパイル使用メモリ 211,552 KB
最終ジャッジ日時 2025-01-16 08:13:53
ジャッジサーバーID
（参考情報） 		judge3 / judge2
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ファイルパターン 結果
sample AC * 3
other AC * 34
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ソースコード

diff # 

#include <bits/stdc++.h>
#define REP(i, n) for(int i = 0;i < n;i++)
#define ll long long
using namespace std;
typedef pair<int, int> P;
typedef pair<ll,ll> LP;
const int dx[8] = {1, 0, -1, 0, 1, -1, -1, 1};
const int dy[8] = {0, 1, 0, -1, 1, 1, -1, -1};
const int INF = 1000000000;
const ll LINF = 1000000000000000000;//1e18
const double PI = acos(-1.0);
const double EPS = 1e-10;

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

/*  ----------------------- DEBUG FUNCTION ---------------------------- */
#define DUMPOUT cerr
void dump_function() { DUMPOUT << ' '; }
void dump_function(bool a) { DUMPOUT << a; }
void dump_function(int a) { DUMPOUT << a; }
void dump_function(long long a) { DUMPOUT << a; }
void dump_function(char a) { DUMPOUT << a; }
void dump_function(string &a) { DUMPOUT << a; }
void dump_function(double a) { DUMPOUT << a; }
template <class T> void dump_function(const vector<T> &);
template <class T, size_t size> void dump_function(const array<T, size> &);
template <class T, class L> void dump_function(const pair<T, L> &p);
template <class T, size_t size> void dump_function(const T (&)[size]);
template <class T> void dump_function(const vector<T> &a) {
    if(a.empty()) return;
    dump_function(a[0]);
    for(auto i = a.begin(); ++i != a.end();) {
        DUMPOUT << " ";
        dump_function(*i);
    }
    DUMPOUT << endl;
}
template <class T> void dump_function(const deque<T> &a) {
    if(a.empty()) return;
    dump_function(a[0]);
    for(auto i = a.begin(); ++i != a.end();) {
        DUMPOUT << " ";
        dump_function(*i);
    }
}
template <class T, size_t size> void dump_function(const array<T, size> &a) {
    dump_function(a[0]);
    for(auto i = a.begin(); ++i != a.end();) {
        DUMPOUT << " ";
        dump_function(*i);
    }
}
template <class T, class L> void dump_function(const pair<T, L> &p) {
    DUMPOUT << '(';
    dump_function(p.first);
    DUMPOUT << ",";
    dump_function(p.second);
    DUMPOUT << ')';
}
template <class T> void dump_function(set<T> &x) {
    for(auto e : x) dump_function(e), DUMPOUT << " ";
    DUMPOUT << endl;
}
template <class T> void dump_function(multiset<T> &x) {
    for(auto e : x) dump_function(e), DUMPOUT << " ";
    DUMPOUT << endl;
}
template <class T, size_t size> void dump_function(const T (&a)[size]) {
    dump_function(a[0]);
    for(auto i = a; ++i != end(a);) {
        DUMPOUT << " ";
        dump_function(*i);
    }
}
template <class T> void dump_function(const T &a) { DUMPOUT << a; }
int dump_out() {
    DUMPOUT << '\n';
    return 0;
}
template <class T> int dump_out(const T &t) {
    dump_function(t);
    DUMPOUT << '\n';
    return 0;
}
template <class Head, class... Tail> int dump_out(const Head &head, const Tail &... tail) {
    dump_function(head);
    DUMPOUT << ' ';
    dump_out(tail...);
    return 0;
}

#ifdef DEBUG_
#define dump(x)                                                                                                                                               \
    DUMPOUT << #x << ": ";                                                                                                                                        \
    dump_function(x);                                                                                                                                                  \
    DUMPOUT << endl;
void dumps() {}
template <class T> void dumps(const T &t) {
    dump_function(t);
    DUMPOUT << " ";
}
template <class Head, class... Tail> void dumps(const Head &head, const Tail &... tail) {
    dump_function(head);
    DUMPOUT << ' ';
    dump_out(tail...);
}
#else
#define dump(x)
template <class... T> void dumps(const T &...) {}
#endif
/*  ----------------------- DEBUG FUNCTION ---------------------------- */

template<int MOD> struct Fp {
    long long val;
    constexpr Fp(long long v = 0) noexcept : val(v % MOD) {
        if (val < 0) val += MOD;
    }
    constexpr int getmod() const { return MOD; }
    constexpr Fp operator - () const noexcept {
        return val ? MOD - val : 0;
    }
    constexpr Fp operator + (const Fp& r) const noexcept { return Fp(*this) += r; }
    constexpr Fp operator - (const Fp& r) const noexcept { return Fp(*this) -= r; }
    constexpr Fp operator * (const Fp& r) const noexcept { return Fp(*this) *= r; }
    constexpr Fp operator / (const Fp& r) const noexcept { return Fp(*this) /= r; }
    constexpr Fp& operator += (const Fp& r) noexcept {
        val += r.val;
        if (val >= MOD) val -= MOD;
        return *this;
    }
    constexpr Fp& operator -= (const Fp& r) noexcept {
        val -= r.val;
        if (val < 0) val += MOD;
        return *this;
    }
    constexpr Fp& operator *= (const Fp& r) noexcept {
        val = val * r.val % MOD;
        return *this;
    }
    constexpr Fp& operator /= (const Fp& r) noexcept {
        long long a = r.val, b = MOD, u = 1, v = 0;
        while (b) {
            long long t = a / b;
            a -= t * b, swap(a, b);
            u -= t * v, swap(u, v);
        }
        val = val * u % MOD;
        if (val < 0) val += MOD;
        return *this;
    }
    constexpr bool operator == (const Fp& r) const noexcept {
        return this->val == r.val;
    }
    constexpr bool operator != (const Fp& r) const noexcept {
        return this->val != r.val;
    }
    friend constexpr istream& operator >> (istream& is, Fp<MOD>& x) noexcept {
        is >> x.val;
        x.val %= MOD;
        if (x.val < 0) x.val += MOD;
        return is;
    }
    friend constexpr ostream& operator << (ostream& os, const Fp<MOD>& x) noexcept {
        return os << x.val;
    }
    friend constexpr Fp<MOD> modpow(const Fp<MOD>& r, long long n) noexcept {
        if (n == 0) return 1;
        auto t = modpow(r, n / 2);
        t = t * t;
        if (n & 1) t = t * r;
        return t;
    }
    friend constexpr Fp<MOD> modinv(const Fp<MOD>& r) noexcept {
        long long a = r.val, b = MOD, u = 1, v = 0;
        while (b) {
            long long t = a / b;
            a -= t * b, swap(a, b);
            u -= t * v, swap(u, v);
        }
        return Fp<MOD>(u);
    }
};

template<class T> struct BiCoef {
    vector<T> fact_, inv_, finv_;
    constexpr BiCoef() {}
    constexpr BiCoef(int n) noexcept : fact_(n, 1), inv_(n, 1), finv_(n, 1) {
        init(n);
    }
    constexpr void init(int n) noexcept {
        fact_.assign(n, 1), inv_.assign(n, 1), finv_.assign(n, 1);
        int MOD = fact_[0].getmod();
        for(int i = 2; i < n; i++){
            fact_[i] = fact_[i-1] * i;
            inv_[i] = -inv_[MOD%i] * (MOD/i);
            finv_[i] = finv_[i-1] * inv_[i];
        }
    }
    constexpr T com(int n, int k) const noexcept {
        if (n < k || n < 0 || k < 0) return 0;
        return fact_[n] * finv_[k] * finv_[n-k];
    }
    constexpr T fact(int n) const noexcept {
        if (n < 0) return 0;
        return fact_[n];
    }
    constexpr T inv(int n) const noexcept {
        if (n < 0) return 0;
        return inv_[n];
    }
    constexpr T finv(int n) const noexcept {
        if (n < 0) return 0;
        return finv_[n];
    }
    constexpr T perm(int n, int k) const noexcept {
        if (n < k || n < 0 || k < 0) return 0;
        return fact_[n] * finv_[n-k];
    }
};

/* ----------------------------- MOD ----------------------------------- */
const int MOD = 1000000007;
const int MOD2 = 998244353;
using mint = Fp<MOD2>;
BiCoef<mint> bc;
// using vec = vector<mint>;
// using mat = vector<vec>;
/* ----------------------------- MOD ----------------------------------- */

/*  ----------------------- AtCoder Library ---------------------------- */
// #include <atcoder/all>
// using namespace atcoder;
/*  ----------------------- AtCoder Library ---------------------------- */

template <class Abel> struct BIT {
    const Abel UNITY_SUM = 0;                       // to be set
    vector<Abel> dat;

    /* [1, n] */
    BIT(int n) : dat(n + 1, UNITY_SUM) { }
    void init(int n) { dat.assign(n + 1, UNITY_SUM); }

    /* a is 1-indexed */
    inline void add1(int a, Abel x) {
        for (int i = a; i < (int)dat.size(); i += i & -i)
            dat[i] = dat[i] + x;
    }

    /* [1, a], a is 1-indexed */
    inline Abel sum1(int a) {
        Abel res = UNITY_SUM;
        for (int i = a; i > 0; i -= i & -i)
            res = res + dat[i];
        return res;
    }

    /* [a, b), a and b are 1-indexed */
    inline Abel sum1(int a, int b) {
        return sum(b - 1) - sum(a - 1);
    }

    /* a is 0-indexed */
    inline void add(int a, Abel x){
        add1(a + 1, x);
    }

    /* [0, a), a is 0-indexed */
    inline Abel sum(int a){
        return sum1(a);
    }

    /* [a, b), a is 0-indexed */
    inline Abel sum(int a, int b){
        return sum1(b) - sum1(a);
    }

    /* get k-th element (k is 0-indexed) */
    int kth_element(long long k) {
        ++k;
        int res = 0;
        int N = 1; while (N < (int)dat.size()) N *= 2;
        for (int i = N / 2; i > 0; i /= 2) {
            if (res + i < (int)dat.size() && dat[res + i] < k) {
                k = k - dat[res + i];
                res = res + i;
            }
        }
        return res + 1;
    }

    /* debug */
    void print() {
        for (int i = 1; i < (int)dat.size(); ++i) cout << sum1(i, i + 1) << ",";
        cout << endl;
    }
};

template<typename T>
struct Compress {
	vector<T> v;
	Compress() {}
	Compress(vector<T> _v) :v(_v) { build(); }

	void add(T x) {
		v.emplace_back(x);
	}

	void build() {
		sort(v.begin(), v.end());
		v.erase(unique(v.begin(), v.end()), v.end());
	}
	void build(vector<T> _v) {
		v = _v;
		sort(v.begin(), v.end());
		v.erase(unique(v.begin(), v.end()), v.end());
	}
	int get(T x) {
		return lower_bound(v.begin(), v.end(), x) - v.begin();
	}

	T& operator[](int i) { return v[i]; }


	int size() {
		return (int)v.size();
	}
};

void solve(){
    ll N;
    cin >> N;
    vector<ll> A(N);
    REP(i,N) cin >> A[i];
    Compress<ll> cmp(A);
    cmp.build();
    BIT<mint> left(N), right(N);
    BIT<mint> left_sum(N), right_sum(N);
    vector<mint> imos(N + 10);
    left.add(cmp.get(A[0]), 1);
    left_sum.add(cmp.get(A[0]), A[0]);
    for(int i=1;i<N;i++){
        right.add(cmp.get(A[i]), 1);
        right_sum.add(cmp.get(A[i]), A[i]);
    }
    mint ans = 0;
    for(int i=1;i<N-1;i++){
        right.add(cmp.get(A[i]), -1);
        right_sum.add(cmp.get(A[i]), -A[i]);
        mint left_cnt = left.sum(cmp.get(A[i])+1, N);
        mint right_cnt = right.sum(cmp.get(A[i]));
        mint lsum = left_sum.sum(cmp.get(A[i])+1, N);
        mint rsum = right_sum.sum(cmp.get(A[i]));
        if(right_cnt.val > 0 and left_cnt.val > 0){
            ans += lsum * right_cnt;
            ans += rsum * left_cnt;
            ans += mint(A[i]) * left_cnt * right_cnt;
        }
        left.add(cmp.get(A[i]), 1);
        left_sum.add(cmp.get(A[i]), A[i]);
        // dumps(i, ans, lsum, rsum, left_cnt, right_cnt);
        // dump(ans);
    }
    cout << ans << endl;
}

int main(){
    cin.tie(0);
    ios::sync_with_stdio(false);
    solve();
    // int T; cin >> T; REP(t,T) solve();
}
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