Submission #921729

#	Time	Username	Problem	Language	Result	Execution time	Memory
921729		Alebn	Fancy Fence (CEOI20_fancyfence)	C++14	0 / 100	1 ms	600 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;
    for(int i = 0; i < n; i++) {
        res = (res + f(h[i], suffixWSum[i])) % MOD;
        if(i != 0) res = (res - f(h[i-1], suffixWSum[i])) % MOD;
        if(res < 0) res = (res + MOD) % MOD;
    }
    res = (res + f(h[n-1], suffixWSum[n-1])) % MOD;
    if(n > 1) res = (res - f(h[n-2], suffixWSum[n-2])) % MOD;
    if(res < 0) res = (res + MOD) % MOD;
    cout << res << "\n";
}

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