Submission #851283

#	Time	Username	Problem	Language	Result	Execution time	Memory
851283		Jawad_Akbar_JJ	Fancy Fence (CEOI20_fancyfence)	C++14	0 / 100	10 ms	8024 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;
}

signed main(){
	int n;
	cin>>n;
	for (int i=1;i<=n;i++)
		cin>>h[i];
	int ans = 0;
	for (int i=1;i<=n;i++){
		cin>>w[i];
		int a = (w[i]*(w[i]+1));
		a = a % mod;
		a = mod_inv(2) * a;
		ans += a;
		ans %= mod;
		if (h[i]==2)
			ans += 2*a;
		ans %= mod;
	}
	for (int i=n;i>=1;i--){
		for (int j=1;j<=h[i];j++){
			r[i][j] = r[i+1][j];
			ans += (r[i][j]*j)%mod;
			ans %= mod;
			r[i][j] = r[i+1][j] + w[i];
			r[i][j] %= mod;
			// cout<<"At "<<i<<" "<<j<<" added "<<r[i][j]*j<<endl;
		}
	}
	cout<<ans<<endl;
}

• 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