Submission #703392

#	Time	Username	Problem	Language	Result	Execution time	Memory
703392		Darren0724	Fancy Fence (CEOI20_fancyfence)	C++17	30 / 100	25 ms	4928 KiB

fancyfence

#include<bits/stdc++.h>
using namespace std;
#define int long long
#define pii pair<int,int>
#define all(x) x.begin(),x.end()
const int mod=1e9+7;
int cal(int left,int right,int up,int down){
    int width=right-left+1;
    width%=mod;
    int ans=width*(width-1)/2;
    ans%=mod;
    int tmp=up*(up+1)-down*(down+1);
    tmp/=2;
    tmp%=mod;
    //cout<<left<<' '<<right<<' '<<up<<' '<<down<<' '<<ans*tmp<<endl;
    return ans*tmp%mod;
}
signed main(){
    ios_base::sync_with_stdio(false);
    cin.tie(0);
    int n;cin>>n;
    vector<int> a(n+1),b(n+1);
    for(int i=1;i<=n;i++){
        cin>>a[i];
    }
    for(int i=1;i<=n;i++){
        cin>>b[i];
        b[i]+=b[i-1];
    }
    int ans=0;
    vector<int> v;
    v.push_back(0);
    for(int i=1;i<=n;i++){
        while(a[i]<a[v.back()]){
            //cout<<"OK"<<endl;
            int tmp=v.back();
            v.pop_back();
            ans+=cal(b[tmp-1],b[i-1],a[tmp],min(a[i],a[v.back()]));
            ans%=mod;
        }
        if(a[i]>a[v.back()]){
            v.push_back(i);
        }
    }
    while(v.size()>1){
        int tmp=v.back();
        v.pop_back();
        ans+=cal(b[tmp-1],b[n],a[tmp],a[v.back()]);
        ans%=mod;
    }
    cout<<ans<<endl;

    return 0;
}

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