Submission #680349

#	Time	Username	Problem	Language	Result	Execution time	Memory
680349		peijar	Fancy Fence (CEOI20_fancyfence)	C++17	12 / 100	1 ms	340 KiB

fancyfence

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

namespace std {
template <typename T> ostream &operator<<(ostream &out, const vector<T> &vec) {
  out << "[";
  for (int i = 0; i < (int)vec.size(); ++i) {
    out << vec[i];
    if (i + 1 < (int)vec.size())
      out << ", ";
  }
  return out << "]";
}
} // namespace std

void dbg_out() { cout << endl; }
template <typename Head, typename... Tail> void dbg_out(Head H, Tail... T) {
  cout << ' ' << H;
  dbg_out(T...);
}

#ifdef DEBUG
#define dbg(...) cout << "(" << #__VA_ARGS__ << "):", dbg_out(__VA_ARGS__)
#else
#define dbg(...)
#endif

template <const int32_t MOD> struct ModInt {
  int32_t x;
  ModInt() : x(0) {}
  ModInt(long long u) : x(u % MOD) {
    if (x < 0)
      x += MOD;
  }
  friend bool operator==(const ModInt &a, const ModInt &b) {
    return a.x == b.x;
  }
  friend bool operator!=(const ModInt &a, const ModInt &b) {
    return a.x != b.x;
  }
  friend bool operator<(const ModInt &a, const ModInt &b) { return a.x < b.x; }
  friend bool operator>(const ModInt &a, const ModInt &b) { return a.x > b.x; }
  friend bool operator<=(const ModInt &a, const ModInt &b) {
    return a.x <= b.x;
  }
  friend bool operator>=(const ModInt &a, const ModInt &b) {
    return a.x >= b.x;
  }
  static ModInt sign(long long k) {
    return ((k & 1) ? ModInt(MOD - 1) : ModInt(1));
  }

  ModInt &operator+=(const ModInt &m) {
    x += m.x;
    if (x >= MOD)
      x -= MOD;
    return *this;
  }
  ModInt &operator-=(const ModInt &m) {
    x -= m.x;
    if (x < 0LL)
      x += MOD;
    return *this;
  }
  ModInt &operator*=(const ModInt &m) {
    x = (1LL * x * m.x) % MOD;
    return *this;
  }

  friend ModInt operator-(const ModInt &a) {
    ModInt res(a);
    if (res.x)
      res.x = MOD - res.x;
    return res;
  }
  friend ModInt operator+(const ModInt &a, const ModInt &b) {
    return ModInt(a) += ModInt(b);
  }
  friend ModInt operator-(const ModInt &a, const ModInt &b) {
    return ModInt(a) -= ModInt(b);
  }
  friend ModInt operator*(const ModInt &a, const ModInt &b) {
    return ModInt(a) *= ModInt(b);
  }

  static long long fp(long long u, long long k) {
    long long res = 1LL;
    while (k > 0LL) {
      if (k & 1LL)
        res = (res * u) % MOD;
      u = (u * u) % MOD;
      k /= 2LL;
    }
    return res;
  }

  static constexpr int mod() { return MOD; }

  ModInt fastpow(long long k) { return ModInt(fp(x, k)); }
  ModInt inv() {
    assert(x);
    return ModInt(fp(x, MOD - 2));
  }
  ModInt &operator/=(const ModInt &m) { return *this *= ModInt(m).inv(); }
  friend ModInt operator/(const ModInt &a, const ModInt &b) {
    return ModInt(a) *= ModInt(b).inv();
  }

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

const int MOD = 1e9 + 7;
using Mint = ModInt<MOD>;

signed main(void) {
  ios_base::sync_with_stdio(false);
  cin.tie(0);

  int N;
  cin >> N;
  vector<int> h(N), w(N);
  vector<int> prv(N), nxt(N);
  for (int &x : h)
    cin >> x;
  for (int &x : w)
    cin >> x;
  vector<int> prefW(N + 1);
  for (int i = 0; i < N; ++i)
    prefW[i + 1] = prefW[i] + w[i];
  for (int i = 0; i < N; ++i) {
    prv[i] = i - 1;
    while (prv[i] >= 0 and h[prv[i]] > h[i])
      prv[i] = prv[prv[i]];
  }
  for (int i = N - 1; i >= 0; --i) {
    nxt[i] = i + 1;
    while (nxt[i] < N and h[nxt[i]] >= h[i])
      nxt[i] = nxt[nxt[i]];
  }

  Mint sol = 0;
  for (int i = 0; i < N; ++i) {
    int L = prv[i] + 1;
    int R = nxt[i];
    // [L, R)
    Mint cntL = prefW[i] - prefW[L];
    Mint cntR = prefW[R] - prefW[i + 1];
    sol += Mint(h[i]) * (h[i] + Mint(1)) / 2 *
           ((cntL + 1) * (cntR + 1) + (w[i] - 1) * (cntL + cntR + 2));
  }
  cout << sol << endl;
}

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