Submission #921467

#	Time	Username	Problem	Language	Result	Execution time	Memory
921467		Alebn	Fancy Fence (CEOI20_fancyfence)	C++14	15 / 100	60 ms	4692 KiB

fancyfence

#include <bits/stdc++.h>
#define int long long

using namespace std;

const int MOD = 1e9+7, INV = 250000002;

int f(int n, int m) {
    return n * m % MOD * (n + 1) % MOD * (m + 1) % MOD * INV % MOD;
}

signed main() {
    //input and sum
    int n;
    cin >> n;
    vector<int> h(n), w(n), suffixWSum(n);
    for(int i = 0; i < n; i++) cin >> h[i];
    for(int i = 0; i < n; i++) cin >> w[i];
    for(int i = n-1; i > -1; i--) suffixWSum[i] = (w[i] + (i == n-1 ? 0 : suffixWSum[i+1])) % MOD;
    //linearily go over and compute result
    int res = 0, m = suffixWSum[0], pastH = 0;
    for(int i = 0; i < n; i++) {
        if(i != 0 && h[i-1] < h[i]) {
            res = (res + f(h[i-1], m) - f(pastH, m)) % MOD;
            //cout << h[i-1] << " " << m << "\n";
            m = suffixWSum[i], pastH = h[i-1];
        }
    }
    //cout << h[n-1] << " " << m << "\n";
    res = (res + f(h[n-1], m) - f(pastH, m)) % MOD;
    cout << res << "\n";
}

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