제출 #701497

#	제출 시각	아이디	문제	언어	결과	실행 시간	메모리
701497		PCTprobability	Fancy Fence (CEOI20_fancyfence)	C++17	0 / 100	1090 ms	340 KiB

fancyfence

#include <bits/stdc++.h>
using namespace std;
using ll = long long;
const ll mod = 1000000007;
#define fi first
#define se second
int main(){
  ll n;
  cin>>n;
  vector<ll> a(n),b(n);
  for(int i=0;i<n;i++) cin>>a[i];
  for(int i=0;i<n;i++) cin>>b[i];
  ll ans=0;
  for(int i=0;i<n;i++) (ans+=((b[i]*(b[i]+1))/2%mod)*((a[i]*(a[i]+1)/2)%mod))%=mod;
  ans%=mod;
  vector<pair<ll,ll>> s;
  ll sum=0;
  //高さ、幅
  for(int i=0;i<n;i++){
    if(i==0){
      s.push_back({a[i],b[i]});
      sum+=(a[i]*(a[i]+1)/2)%mod*b[i];
      sum%=mod;
      continue;
    }
    ll sum2=b[i];
    while(s.size()&&s.back().fi>a[i]){
      sum2+=s.back().se;
      sum-=(s.back().fi*(s.back().fi+1)/2%mod)*b[i];
      sum%=mod;
      sum+=mod;
      sum%=mod;
    }
    ans+=sum*b[i];
    ans%=mod;
    s.push_back({a[i],sum2%mod});
  }
  cout<<ans<<endl;
}

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