UVa 10012 - How Big Is It?

#include <iostream>
#include <algorithm>
#include <cstring>
#include <cstdlib>
#include <cstdio>
#include <cmath>
using namespace std;
int vis[8], num;
double a[8], b[8], d[8], _max;
void check(int cur) // 求新圆放置的位置
{
d[cur] = b[cur];
double dis1, dis2, dis;
for(int i = cur - 1; i >= 0; i--)
{
dis1 = b[i] + b[cur];
dis2 = b[i] - b[cur];
dis = d[i] + sqrt(dis1 * dis1 - dis2 * dis2);
if(dis > d[cur])
d[cur] = dis;
}
}
void dfs(int cur, double sum) // dfs，全排列
{
if(sum > _max)
return ;
if(cur == num)
{
double l = b[0];
sum += b[cur - 1];
for(int i = 0; i < num - 1; i++)
if(d[i] + b[i] > sum)
sum = d[i] + b[i];
for(int i = 1; i < num; i++)
if(b[i] - d[i] > l)
l = b[i] - d[i];
sum += l;
if(sum < _max)
_max = sum;
return ;
}
for(int i = 0; i < num; i++)
if(!vis[i])
{
vis[i] = 1;
b[cur] = a[i];
check(cur);
dfs(cur + 1, d[cur]);
vis[i] = 0;
}
}
int main()
{
#ifdef test
freopen("sample.txt", "r", stdin);
#endif
int n;
scanf("%d", &n);
memset(vis, 0, sizeof(vis));
while(n--)
{
_max = 0x7FFFFFFF;
scanf("%d", &num);
for(int i = 0; i < num; i++)
scanf("%lf", &a[i]);
for(int i = 0; i < num; i++)
{
vis[i] = 1;
d[0] = 0;
b[0] = a[i];
dfs(1, 0);
vis[i] = 0;
}
printf("%.3lf\n", _max);
}
return 0;
}