Submission #1006942

#	Time	Username	Problem	Language	Result	Execution time	Memory
1006942		Hanksburger	Fancy Fence (CEOI20_fancyfence)	C++17	100 / 100	26 ms	6104 KiB

fancyfence

#include <bits/stdc++.h>
using namespace std;
long long h[100005], w[100005], mod=1e9+7, inv2=5e8+4;
vector<pair<long long, long long> > vec;
int main()
{
    ios::sync_with_stdio(0);
    cin.tie(0);
    cout.tie(0);
    long long n, cur=0, ans=0;
    cin >> n;
    for (long long i=1; i<=n; i++)
        cin >> h[i];
    for (long long i=1; i<=n; i++)
        cin >> w[i];
    vec.push_back({-1, 0});
    vec.push_back({0, 0});
    for (long long i=1; i<=n+1; i++)
    {
        while (vec[vec.size()-2].first>=h[i])
        {
            long long x=(cur-vec[vec.size()-1].second+mod)%mod*(cur-vec[vec.size()-1].second+1+mod)%mod*inv2%mod;
            long long y=(vec[vec.size()-1].first+vec[vec.size()-2].first+1)%mod*(vec[vec.size()-1].first-vec[vec.size()-2].first+mod)%mod*inv2%mod;
            ans=(ans+x*y)%mod;
            vec.pop_back();
        }
        if (vec[vec.size()-1].first>h[i])
        {
            long long x=(cur-vec[vec.size()-1].second+mod)%mod*(cur-vec[vec.size()-1].second+1+mod)%mod*inv2%mod;
            long long y=(vec[vec.size()-1].first+h[i]+1)%mod*(vec[vec.size()-1].first-h[i]+mod)%mod*inv2%mod;
            ans=(ans+x*y)%mod;
            vec[vec.size()-1].first=h[i];
        }
        else
            vec.push_back({h[i], cur});
        cur=(cur+w[i])%mod;
    }
    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: 27 / 27