Submission #702657

#	Time	Username	Problem	Language	Result	Execution time	Memory
702657		a_aguilo	Fancy Fence (CEOI20_fancyfence)	C++14	100 / 100	99 ms	5448 KiB

fancyfence

#include<bits/stdc++.h>
 
using namespace std;
 
int n;
int MOD = 1e9 + 7;
 
long long calcOwnRectangles(long long int h, long long int w, long long int addition){
	long long chooseH = (h*(h+1)/2)%MOD;
	long long chooseW = ((w*(w+1)/2)%MOD + (addition*w)%MOD )%MOD;
	long long ans = (chooseH*chooseW)%MOD;
	return ans;
}
 
long long getEndings(long long h, long long w){
	long long WOptions = w;
	long long HOptions = (h*(h+1)/2)%MOD;
	long long ans = (WOptions*HOptions)%MOD;
	return ans;
}
 
int main(){
	cin >> n;
	int heights[n];
	int widths[n];
	long long dp[n];
	long long int ans = 0;
	for(int i = 0; i < n; ++i) cin >> heights[i];
	for(int i = 0; i < n; ++i) cin >> widths[i];
	vector<pair<long long int, long long int>> MyStack;
	MyStack.reserve(n);
	for(int i = 0; i < n; ++i){
		long long int myH = heights[i];
		long long int myW = widths[i];
		long long addW = 0;
		int lPos = MyStack.size()-1;
		while(lPos >= 0 and MyStack[lPos].first > myH){
			addW += MyStack[lPos].second;
			addW %= MOD;
			MyStack.pop_back();
			lPos = MyStack.size()-1;
		}
		MyStack.push_back({myH, myW+addW});
		long long indepRectangles = calcOwnRectangles(myH, myW, addW);
		ans += indepRectangles;
		ans %= MOD;
		//cout << myH << " " << myW << " "<< ans << endl;
		dp[MyStack.size()-1] = getEndings(myH, (myW+addW)%MOD);
		if(MyStack.size() == 1){
			//Este es el primero
			continue;
		}else{
			//Este NO es el primero --> para los rectángulos se pueden continuar los que acaban en el anterior
			ans += (dp[MyStack.size()-2]*myW)%MOD;
			ans %= MOD;
			//Tambien se puede hacer que el numero de los que acaban en esta posicion incorpore los que acaban en la anterior
			dp[MyStack.size()-1] += dp[MyStack.size()-2];
			dp[MyStack.size()-1] %= MOD;
		}
		//cout << myH << " " << ans << endl;
 
	}
	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