Submission #1002123

#	Time	Username	Problem	Language	Result	Execution time	Memory
1002123		alecurse	Fancy Fence (CEOI20_fancyfence)	C++17	12 / 100	1 ms	600 KiB

fancyfence

#include <bits/stdc++.h>
#define ll long long int
#define mp make_pair
using namespace std;
ll mod = 1e9+7;
int main() {
    ll N;
    cin>>N;
    vector<ll> prefix(N+1);

    vector<ll> H(N+1), W(N+1);
    ll res=0;
    for(ll i=1;i<=N;i++) {
        cin>>H[i];
    }
    for(ll i=1;i<=N;i++) {
        cin>>W[i];
        prefix[i]=prefix[i-1]+W[i];
    }
   vector<pair<ll,ll> > v(N);
   set<ll> s;
   for(ll i=1;i<=N;i++) {
    s.insert(i);
    v[i-1]=mp(H[i],i);
   }
   sort(v.rbegin(),v.rend());
    s.insert(0);
   s.insert(N+1);
   for(ll t=0;t<N;t++) {
        ll index=v[t].second;
        s.erase(index);
        auto it= s.upper_bound(index);
        ll wd = prefix[*it-1]-prefix[index];
        it=prev(it,1);
        ll ws = prefix[index-1]-prefix[*it];
        ll w = W[index];
        ll h = H[index];
        ll sum=h*(h+(ll)1)/(ll)2;
        ll sumw=w*(w+(ll)1)/(ll)2;
        sum%=mod;
        sumw%=mod;
        ll toadd=0;
        toadd+=(ws*w)%mod;
        toadd%=mod;
        toadd+=(wd*w)%mod;
        toadd%=mod;
        toadd+=(wd*ws)%mod;
        toadd%=mod;
        toadd+=sumw;
        toadd%=mod;
        toadd*=sum;
        toadd%=mod;
        res+=toadd;
        res%=mod;
   }    
  
    cout<<res;
}

• 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