Submission #887293

#	Time	Username	Problem	Language	Result	Execution time	Memory
887293		fanwen	Fancy Fence (CEOI20_fancyfence)	C++17	100 / 100	36 ms	19544 KiB

fancyfence

#include <bits/stdc++.h>

#define fi first
#define se second
#define file(name) if (fopen(name".inp", "r")) { freopen(name".inp", "r", stdin); freopen(name".out", "w", stdout); }

using namespace std;

template <int Mod>
struct Modular {
private :
    int val;
    static int inverse(int a, int b) {
        a %= b;
        assert(a);
        if(a == 1) return 1;
        return int(b - (long long) inverse(b, a) * (long long) b / a);
    }
public :
    Modular(long long x = 0) : val(x % Mod) { if(val < 0) val += Mod; }

    friend bool operator == (const Modular &a, const Modular &b) { return a.val == b.val; }
    friend bool operator != (const Modular &a, const Modular &b) { return a.val != b.val; }

    Modular& operator = (const long long &x) { val = x % Mod; if(val < 0) val += Mod; return *this; }
    Modular& operator = (const Modular &x) { val = x.val; return *this; }

    friend istream & operator >> (istream &in, Modular &a) { long long x; in >> x; a = Modular(x); return in; }
    friend ostream & operator << (ostream &out, const Modular &a) { return out << a.val; }

    explicit operator int() const { return val; }
    explicit operator bool() const { return val > 0; }

    Modular inv() const {
        Modular res;
        res.val = inverse(val, Mod);
        return res;
    }

    Modular operator ++() { (*this) += 1; return *this; }
    Modular operator --() { (*this) -= 1; return *this; }
    Modular operator ++(int) { (*this) += 1; return *this - 1; }
    Modular operator --(int) { (*this) -= 1; return *this + 1; }

    Modular operator + () const { return *this; }
    Modular operator - () const {
        Modular res;
        res.val = (val ? Mod - val : 0);
        return res;
    }

    Modular& operator += (const Modular &a) {
        val += a.val;
        if(val >= Mod) val -= Mod;
        return *this;
    }
    Modular& operator -= (const Modular &a) {
        val -= a.val;
        if(val < 0) val += Mod;
        return *this;
    }
    Modular& operator *= (const Modular &a) {
        val = 1LL * val * a.val % Mod;
        return *this;
    }
    Modular& operator /= (const Modular &a) {
        (*this) *= a.inv();
        return *this;
    }
    friend Modular operator + (const Modular &a, const Modular &b) { return Modular(a) += b; }
    friend Modular operator - (const Modular &a, const Modular &b) { return Modular(a) -= b; }
    friend Modular operator * (const Modular &a, const Modular &b) { return Modular(a) *= b; }
    friend Modular operator / (const Modular &a, const Modular &b) { return Modular(a) /= b; }
};

// const int Mod = 998244353;
// const int Mod = 1e9 + 9; // 1000000009
const int Mod = 1e9 + 7; // 1000000007

using Modint = Modular <Mod>;

template <class T> T pow(T a, long long b) {
    T ans = 1, mul = a;
    for (; b; b >>= 1) {
        if(b & 1LL) ans *= mul;
        mul *= mul;
    }
    return ans;
}

template<class T, T (*merge) (T, T)>
struct sparse_table {
    vector <vector <T>> q;
    int n;

    sparse_table() {}
    sparse_table(const vector <T> &v) : n((int) v.size()) {
        q.push_back(v);
        for (int k = 1; (1 << k) <= n; ++k) {
            q.emplace_back(n - (1 << k) + 1);
            for (int i = 0; i + (1 << k) <= n; ++i) {
                q[k][i] = merge(q[k - 1][i], q[k - 1][i + (1 << (k - 1))]);
            }
        }
    }

    T get(int l, int r) {
        assert(0 <= l && l <= r && r < n);
        int k = 31 - __builtin_clz(r - l + 1);
        return merge(q[k][l], q[k][r - (1 << k) + 1]);
    }
};

const int MAX = 1e5 + 5;

int n;
pair <int, int> a[MAX];

Modint get(int h, int w) {
    return Modint(h) * Modint(h + 1) * Modint(w) * Modint(w + 1) / 4;
}

int merge(int i, int j) {
    return a[i].fi < a[j].fi ? i : j;
}

Modint pref[MAX];

void you_make_it(void) {
    cin >> n;
    for (int i = 1; i <= n; ++i) cin >> a[i].fi;
    for (int i = 1; i <= n; ++i) cin >> a[i].se;
    vector <int> id(n + 1);
    iota(id.begin(), id.end(), 0);
    sparse_table <int, merge> rmq(id);
    for (int i = 1; i <= n; ++i) pref[i] = pref[i - 1] + a[i].se;

    Modint ans = 0;

    auto get = [&] (int l, int r) -> Modint {
        if(l > r) return 0;
        return pref[r] - pref[l - 1];
    };
    function <void(int, int)> solve = [&] (int l, int r) {
        if(l > r) return;

        int mid = rmq.get(l, r);
        Modint tmp = Modint(a[mid].fi) * Modint(a[mid].fi + 1) / 2;
        ans += tmp * get(l, mid) * get(mid, r);
        ans -= tmp * a[mid].se * a[mid].se;
        ans += tmp * (a[mid].se) * (a[mid].se + 1) / 2;
        solve(l, mid - 1);
        solve(mid + 1, r);
    };

    solve(1, n);

    cout << ans;
}

signed main() {

#ifdef LOCAL
    freopen("TASK.inp", "r", stdin);
    freopen("TASK.out", "w", stdout);
#endif
    file("fancyfence");
    auto start_time = chrono::steady_clock::now();

    cin.tie(0), cout.tie(0) -> sync_with_stdio(0);

    you_make_it();

    auto end_time = chrono::steady_clock::now();

    cerr << "\nExecution time : " << chrono::duration_cast <chrono::milliseconds> (end_time - start_time).count() << "[ms]" << endl;

    return (0 ^ 0);
}

// Dream it. Wish it. Do it.

Compilation message (stderr)

fancyfence.cpp: In function 'int main()':
fancyfence.cpp:5:57: warning: ignoring return value of 'FILE* freopen(const char*, const char*, FILE*)' declared with attribute 'warn_unused_result' [-Wunused-result]
    5 | #define file(name) if (fopen(name".inp", "r")) { freopen(name".inp", "r", stdin); freopen(name".out", "w", stdout); }
      |                                                  ~~~~~~~^~~~~~~~~~~~~~~~~~~~~~~~
fancyfence.cpp:167:5: note: in expansion of macro 'file'
  167 |     file("fancyfence");
      |     ^~~~
fancyfence.cpp:5:90: warning: ignoring return value of 'FILE* freopen(const char*, const char*, FILE*)' declared with attribute 'warn_unused_result' [-Wunused-result]
    5 | #define file(name) if (fopen(name".inp", "r")) { freopen(name".inp", "r", stdin); freopen(name".out", "w", stdout); }
      |                                                                                   ~~~~~~~^~~~~~~~~~~~~~~~~~~~~~~~~
fancyfence.cpp:167:5: note: in expansion of macro 'file'
  167 |     file("fancyfence");
      |     ^~~~

• Subtask 1: 0 / 0
• Subtask 2: 12 / 12
• Subtask 3: 13 / 13
• Subtask 4: 15 / 15
• Subtask 5: 15 / 15
• Subtask 6: 18 / 18
• Subtask 7: 27 / 27