Submission #945694

#	Time	Username	Problem	Language	Result	Execution time	Memory
945694		itslq	Fancy Fence (CEOI20_fancyfence)	C++17	73 / 100	33 ms	3032 KiB

fancyfence

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

#define int long long

const int MOD = 1e9 + 7;
const int MOD2 = 2 * MOD;

int md(int x) {
    if (x < 0) return (x % MOD) + MOD;
    if (x < MOD) return x;
    return x % MOD;
}

int md2(int x) {
    if (x < 0) return (x % MOD2) + MOD2;
    if (x < MOD2) return x;
    return x % MOD2;
}

int tri(int x) {
    if (x % 2) return md((x + 1) / 2 * x);
    return md(x / 2 * (x + 1));
}

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

    int N, minH, ans = 0, S = 0;
    bool st3 = 1, st4 = 1, st5 = 1;
    cin >> N;
    vector<int> H(N), W(N);

    for (int i = 0; i < N; i++) {
        cin >> H[i];
        if (H[i] > 2) st3 = 0;
        if (H[i] != H[0]) st4 = 0;
        if (i && H[i] < H[i - 1]) st5 = 0;
    }

    for (int i = 0; i < N; i++) {
        cin >> W[i];
        S = md2(S + W[i]);
    }

    if (st3) {
        vector<int> compH{H[0]}, compW{W[0]};

        for (int i = 1; i < N; i++) {
            if (H[i] == compH.back()) compW.back() = md2(compW.back() + W[i]);
            else {
                compH.push_back(H[i]);
                compW.push_back(W[i]);
            }
        }

        for (int i = 0; i < (signed) compH.size(); i++) {
            if (compH[i] == 2) {
                ans = md(ans + md(2 * tri(compW[i])));
            }
        }

        cout << md(ans + tri(S));
        return 0;
    }

    if (st4) {
        cout << md(tri(S) * tri(H[0]));
        return 0;
    }

    if (st5) {
        for (int i = N - 2; i >= 0; i--) {
            W[i] = md2(W[i] + W[i + 1]);
        }

        for (int i = 0; i < N; i++) {
            ans = md(ans + tri(H[i]) * tri(W[i]));
        }

        for (int i = 0; i < N - 1; i++) {
            ans = md(ans - tri(H[i]) * tri(W[i + 1]));
        }

        cout << ans;
        return 0;
    }

    if (N <= 1000) {
        for (int i = 0; i < N; i++) {
            minH = H[i];
            ans = md(ans + md(H[i] * (H[i] + 1) / 2) * tri(W[i]));
            for (int j = i + 1; j < N; j++) {
                minH = min(minH, H[j]);
                ans = md(ans + md(W[i] * W[j]) * tri(minH));
            }
        }

        cout << ans;
    }
}

• 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: 0 / 27