Submission #851284

#	Time	Username	Problem	Language	Result	Execution time	Memory
851284		Jawad_Akbar_JJ	Fancy Fence (CEOI20_fancyfence)	C++14	30 / 100	177 ms	4692 KiB

fancyfence

#include <bits/stdc++.h>
 
using namespace std;
#define int long long
const int N = 1e5 + 10;
int r[N][3];
int w[N];
int h[N];
int mod = 1e9 + 7;
 
int power(int a,int b){
	if (b==0)
		return 1;
	int ans = power(a,b/2);
	ans = ans*ans;
	ans %= mod;
	if (b%2)
		ans = ans*a;
	return ans%mod;
}
 
int mod_inv(int k){
	return power(k,mod-2);
}
 
int asd(int a){
	int ans = (a*(a+1));
	ans = ans%mod;
	ans = ans*mod_inv(2);
	ans = ans% mod;
	return ans;
}

int answer(int W,int H){
	int ans = asd(W);
	int ans2 = asd(H);
	return (ans*ans2)%mod ;
}

signed main(){
	int n;
	cin>>n;
	for (int i=1;i<=n;i++)
		cin>>h[i];
	int ans = 0;
	int W = 0;
	for (int i=1;i<=n;i++){
		cin>>w[i];
		W += w[i];
		W %= mod;
	}

	for (int i=1;i<=n;i++){
		ans += answer(W,h[i]);
		// cout<<i<<" "<<answer(W,h[i])<<endl;
		ans = ans % mod;
		ans -= answer(W,h[i-1]);
		// cout<<answer(W,h[i-1])<<endl;
		if (ans<0)
			ans += mod;
		W -= w[i];
		if (W<0)
			W += 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