Submission #954064

#	Time	Username	Problem	Language	Result	Execution time	Memory
954064		Sharky	Fancy Fence (CEOI20_fancyfence)	C++17	30 / 100	22 ms	3676 KiB

fancyfence

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

#define int long long
const int mod = 1e9 + 7;

int s(int x) {
    return (x * (x + 1) / 2) % mod;
}

int s(int l, int r) {
    return (s(r) - s(l-1)) % mod;
}

void norm(int& x) {
    x = (x % mod + mod) % mod;
}

int32_t main() {
    ios::sync_with_stdio(0); cin.tie(0);
    int n;
    cin >> n;
    stack<pair<int, int>> st;
    int sum = 0, delta = 0;
    vector<int> H(n+1), W(n+1);
    for (int i = 1; i <= n; i++) cin >> H[i];
    for (int i = 1; i <= n; i++) cin >> W[i];
    for (int i = 1; i <= n; i++) {
        int h = H[i], w = W[i], aw = w;
        while (!st.empty() && st.top().first >= h) {
            auto [ff, ss] = st.top();
            st.pop();
            int nxth = h;
            if (!st.empty() && st.top().first >= h) nxth = st.top().first, st.top().second += ss;
            else aw += ss;
            delta -= (s(nxth + 1, ff) * s(1, ss)) % mod;
            norm(delta);
        }
        // cout << delta << ' ' << h << ' ' << w << '\n';
        st.push({h, aw});
        sum += delta * w + s(h) * s(w);
        norm(sum);
        delta += s(h) * w;
        norm(delta);
        // cout << sum << ' ' << delta << '\n';
    }
    cout << sum << '\n';
}

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