Submission #945612

#	Time	Username	Problem	Language	Result	Execution time	Memory
945612		itslq	Fancy Fence (CEOI20_fancyfence)	C++17	12 / 100	6 ms	600 KiB

fancyfence

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

#define int long long

const int MOD = 1e9 + 7;

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

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

signed main() {
    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 += 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() += W[i];
            else {
                compH.push_back(H[i]);
                compW.push_back(W[i]);
            }
        }

        ans = tri(S);

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

        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;
    }
}

Compilation message (stderr)

fancyfence.cpp: In function 'int main()':
fancyfence.cpp:21:19: warning: variable 'st4' set but not used [-Wunused-but-set-variable]
   21 |     bool st3 = 1, st4 = 1, st5 = 1;
      |                   ^~~
fancyfence.cpp:21:28: warning: variable 'st5' set but not used [-Wunused-but-set-variable]
   21 |     bool st3 = 1, st4 = 1, st5 = 1;
      |                            ^~~

• 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