Crazy WA
In the end, I still had to refer to the internet; it turns out that I need to keep updating the left and right sides.
//============================================================================
// Name : How Big Is It.cpp
// Date : 2013/4/26 1:30:18 PM
// Author : GCA
//============================================================================
#include <iostream>
#include <cstdio>
#include <cstring>
#include <algorithm>
#include <cmath>
#include <climits>
#include <vector>
#include <set>
#include <map>
#include <queue>
#include <cctype>
#include <utility>
using namespace std;
#ifdef ONLINE\_JUDGE
#define ll "%lld"
#else
#define ll "%I64d"
#endif
typedef unsigned int uint;
typedef long long int Int;
#define Set(a,s) memset(a,s,sizeof(a))
#define Write(w) freopen(w,"w",stdout)
#define Read(r) freopen(r,"r",stdin)
#define Pln() printf("\\n")
#define I\_de(x,n)for(int i=0;i<n;i++)printf("%d ",x\[i\]);Pln()
#define De(x)printf(#x"%d\\n",x)
#define For(i,x)for(int i=0;i<x;i++)
#define CON(x,y) x##y
#define Pmz(dp,nx,ny)for(int hty=0;hty<ny;hty++){for(int htx=0;htx<nx;htx++){\\
printf("%d ",dp\[htx\]\[hty\]);}Pln();}
#define M 55
#define PII pair<int,int\>
#define PB push\_back
#define oo INT\_MAX
#define Set\_oo 0x3f
#define Is\_debug true
#define debug(...) if(Is\_debug)printf("DEBUG: "),printf(\_\_VA\_ARGS\_\_)
#define FOR(it,c) for(\_\_typeof((c).begin()) it=(c).begin();it!=(c).end();it++)
#define eps 1e-6
bool xdy(double x,double y){return x>y+eps;}
bool xddy(double x,double y){return x>y-eps;}
bool xcy(double x,double y){return x<y-eps;}
bool xcdy(double x,double y){return x<y+eps;}
int min3(int x,int y,int z){
int tmp=min(x,y);
return min(tmp,z);
}
int max3(int x,int y,int z){
int tmp=max(x,y);
return max(tmp,z);
}
double r\[M\];
bool vis\[M\];
double pos\[M\];
double dfsr\[M\];
double minans;
int n;
void dfs(int depth){
if(depth==n){
double xl=oo;
double xr=0;
for(int i=0;i<n;i++){
xl=min(xl,(pos\[i\]-dfsr\[i\]));
xr=max(xr,(pos\[i\]+dfsr\[i\]));
}
minans=min(minans,xr-xl);
return;
}
for(int i=0;i<n;i++){
if(!vis\[i\]){
dfsr\[depth\]=r\[i\];
pos\[depth\]=0;
for(int j=0;j<depth;j++){
double c=dfsr\[j\]+r\[i\];
double a=fabs(dfsr\[j\]-r\[i\]);
double b=sqrt(c\*c-a\*a);
pos\[depth\]=max(pos\[depth\],b+pos\[j\]);
}
vis\[i\]=1;
dfs(depth+1);
vis\[i\]=0;
}
}
}
int main() {
ios\_base::sync\_with\_stdio(0);
int test;
scanf("%d",&test);
while(test--){
scanf("%d",&n);
for(int i=0;i<n;i++)scanf("%lf",&r\[i\]);
Set(vis,0);
minans=oo;
for(int i=0;i<n;i++){
dfsr\[0\]=r\[i\];
pos\[0\]=r\[i\];
vis\[i\]=1;
dfs(1);
vis\[i\]=0;
}
printf("%.3f\\n",minans);
}
}