Submission #946368

#	Time	Username	Problem	Language	Result	Execution time	Memory
946368		Xiaoyang	Fancy Fence (CEOI20_fancyfence)	C++17	100 / 100	24 ms	5464 KiB

fancyfence

#include <bits/stdc++.h>
using namespace std;
typedef long long ll;
 
#define fi first 
#define se second 
#define pll pair<ll,ll>
#define pb push_back
#define debug(x) cerr<<#x<<"="<<x<<endl;
#define MP make_pair
#define rep(i,a,b) for(ll i=a;i<b;i++)
#define SZ(x) (ll)x.size()
#define ALL(x) x.begin(),x.end()
#define endl "\n"
const ll inf=1e18;
ll lowbit(ll x){return x&(-x);}



const ll mod=1e9+7;
ll c2(ll x){
	return (x*(x-1)/2)%mod;
}
ll rect(ll x,ll y){
	ll xx=(x*(x+1)/2)%mod;
	ll yy=(y*(y+1)/2)%mod;
	return (xx*yy)%mod;
}

const ll maxn=1e5+5;
ll h[maxn],w[maxn],pre[maxn];

ll inc(ll &a,ll b){return a=(a+b)%mod;}
ll dec(ll &a,ll b){return a=(a-b+mod)%mod;}
int main(){
	ios::sync_with_stdio(0);
	cin.tie(0);
	ll n;cin>>n;
	ll sum=0,ans=0;
	rep(i,1,n+1)cin>>h[i];
	rep(i,1,n+1)cin>>w[i];
	
	
	stack<ll>s;
	//monotonically increasing stack 
	rep(i,1,n+1){
		while(!s.empty() and h[i]<=h[s.top()]){
			dec(sum,(c2(h[s.top()]+1)*pre[s.top()])%mod);
			inc(pre[i],pre[s.top()]);
			s.pop();
		}
		s.push(i);
		inc(sum,(c2(h[i]+1)*pre[i])%mod);
		inc(ans,rect(h[i],w[i]));
		inc(ans,(sum*w[i])%mod);
		inc(sum,(c2(h[i]+1)*w[i])%mod);
		
		inc(pre[i],w[i]);
	}
	cout<<ans<<endl;
	return 0;
}

• 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