2018牛客多校第五场A

#include <bits/stdc++.h>
using namespace std;

const double eps = 1e-10;
const int N = 1e5 + 10;
double s[N], c[N], b[N], w[N];
int n, k;

bool OK(double x){
	for(int i = 1; i <= n; i ++){
		w[i] = b[i] - x * s[i];
	}
	sort(w + 1, w + n + 1);
	double ans = 0;
	for(int i = n; i > k; i --){
		ans += w[i];
	}
	if(ans >= 0)
		return true;
	return false;
}

int main(){
	ios :: sync_with_stdio(false);
	cin >> n >> k;
	for(int i = 1; i <= n; i ++){
		cin >> s[i];
	}
	for(int i = 1; i <= n; i ++){
		cin >> c[i];
		b[i] = s[i] * c[i];
	}
	double l = 0.0, r = 100000.0;
	while(r - l > eps){
		double mid = (l + r) / 2;
		if(OK(mid)){
			l = mid;
		}
		else{
			r = mid;
		}
	}
	cout << setiosflags(ios::fixed) << setprecision(8) << l << endl;
	return 0;	
}