제출 #1104135

#	제출 시각	아이디	문제	언어	결과	실행 시간	메모리
1104135		ezzzay	Fancy Fence (CEOI20_fancyfence)	C++14	30 / 100	59 ms	8780 KiB

fancyfence

#include<bits/stdc++.h>
using namespace std;
#define ff first
#define ss second
#define pb push_back
#define int long long
const int N=3e5+5;
int h[N];
int w[N];
int ps[N];
int mod=1e9+7;
int modd(int n){
    return (n%mod+mod)%mod;
}
int calc(int a, int b){
    int f=modd(modd(a*(a+1))*500000004);
    int s=modd(modd(b*(b+1))*500000004);
    return (f*s)%mod;
}
signed main(){
    int n;
    cin>>n;
    for(int i=1;i<=n;i++){
        cin>>h[i];
    }
    for(int i=1;i<=n;i++){
        cin>>w[i];
    }
    int ans=0;
    ps[n+1]=0;
    for(int i=n;i>=1;i--){
        ps[i]=modd(ps[i+1]+w[i]);
       // cout<<ps[i]<<" "<<h[i]<<" ";
      //  cout<<calc(h[i],ps[i])<<" "<<calc(h[i-1],ps[i])<<endl;
        ans+=calc(h[i],ps[i])-calc(h[i-1],ps[i]);
        //cout<<ans<<endl;
        ans=modd(ans);
    }
    cout<<ans;
}

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• Subtask 4: 15 / 15
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