Submission #946347

#	Time	Username	Problem	Language	Result	Execution time	Memory
946347		Xiaoyang	Fancy Fence (CEOI20_fancyfence)	C++17	0 / 100	4 ms	4764 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 tot=0,ans=0;
	rep(i,1,n+1)cin>>h[i];
	rep(i,1,n+1){
		cin>>w[i],inc(tot,w[i]);
		pre[i]=pre[i-1]+w[i];
	}
	
	stack<pll>s;
	//monotonically increasing stack 
	s.push(MP(0ll,0ll));
	rep(i,1,n+1){
		while(!s.empty() and s.top().se>h[i])s.pop();
		ll len=(pre[i-1]-pre[s.top().se]+mod)%mod;
		inc(ans,(((c2(h[i]+1)*len)%mod)*w[i])%mod);
		inc(ans,(s.top().se*w[i])%mod);
		inc(ans,rect(h[i],w[i]));
		s.push(MP(i,(c2(h[i]+1)*(w[i]))%mod));
	}
	cout<<ans<<endl;
	return 0;
}

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