题解 | #学分绩点#

#include <iostream>

using namespace std;

const int N = 20;
double xuefen[N];
double defen[N];

double jidian(double x){
	if(x >= 90 && x <= 100)return 4.0;
	else if(x >= 85 && x <= 89)return 3.7;
	else if(x >= 82 && x <= 84)return 3.3;
	else if(x >= 78 && x <= 81)return 3.0;
	else if(x >= 75 && x <= 77)return 2.7;
	else if(x >= 72 && x <= 74)return 2.3;
	else if(x >= 68 && x <= 71)return 2.0;
	else if(x >= 64 && x <= 67)return 1.5;
	else if(x >= 60 && x <= 63)return 1.0;
	else return 0;
}
int main(){
	int n;
	cin >> n;
	double sum = 0;
	int x = 0;
	for(int i = 0;i < n;i ++)cin >> xuefen[i];
	for(int i = 0;i < n;i ++)cin >> defen[i];
	
	for(int i = 0;i < n;i ++){
		sum += jidian(defen[i]) * xuefen[i];
		x += xuefen[i];
	}
	sum = sum / x;
	printf("%.2f",sum);
	
	return 0;
}