40 pts，求调参数或者降低常数（各种玄学方法都可）。

#include <algorithm>
#include <iostream>
#include <cstring>
#include <cstdio>
#include <ctime>
#include <cmath>

using namespace std;

const int N = 210;
int n, m, w[N], v[N];
double res = -0x3f3f3f3f;

double calc()
{
	int a = 0, b = 0;
	for (int i = 1; i <= m; i ++ )
		a += w[i], b += v[i];
	double tot = (double)a / b;
	if (tot > res) res = tot;
	return tot;
}

void simulate_anneal()
{
	for (double t = 1e6; t >= 1e-4; t *= 0.99)
	{
		double x = calc();
		int a = rand() % m + 1, b = rand() % n + 1;
		swap(w[a], w[b]), swap(v[a], v[b]);
		double y = calc();
		double delta = y - x;
		if (exp(-delta / t) < rand() / RAND_MAX)
			swap(w[a], w[b]), swap(v[a], v[b]);
	}
}

int main()
{
	scanf("%d%d", &n, &m);
	
	for (int i = 1; i <= n; i ++ )
		scanf("%d", &w[i]);
	
	for (int i = 1; i <= n; i ++ )
		scanf("%d", &v[i]);
		
	while (clock() / CLOCKS_PER_SEC <= 0.9) simulate_anneal();
	
	printf("%.3lf\n", res);
	
	return 0;
}