UVA 10012 How Big Is It?

#include<cstdio>
#include<cstring>
#include<iostream>
#include<string>
#include<algorithm>
#include<math.h>
using namespace std;
const int maxn = 10;
int t, n;
int b[maxn], c[maxn];
double a[maxn], w;

double check()
{
	double x[maxn] = { 0 }, m = 0;
	for (int i = 0; i < n; i++)
	{
		x[i] = a[c[i]];
		for (int j = i - 1; j >= 0; j--)
			x[i] = max(x[i], x[j] + 2 * sqrt(a[c[i]] * a[c[j]]));
	}
	for (int i = 0; i < n; i++) m = max(m, x[i] + a[c[i]]);
	return m;
}

void work(int x)
{
	if (x == n)
	{
		double k = check();
		w = min(k, w);
		return;
	}
	for (int i = 1; i <= n;i++)
	if (b[i])
	{
		b[i] = 0;	c[x] = i;
		work(x + 1);
		b[i] = 1;
	}
}

int main()
{
	cin >> t;
	while (t--)
	{
		cin >> n;	w = 1000000000;
		for (int i = 1; i <= n; i++) cin >> a[i], b[i] = 1;
		work(0);
		printf("%.3lf\n", w);
	}
	return 0;
}