#include<iostream>#include<cstdlib>#include<algorithm>#include<cmath>using
namespace std ;class
Circles{public
: int
n ; float
min ; float
x[50]; float
r[50]; float
circlePerm(int
nn , float
rr[50]) { n =nn ; min = 10000000 ; memset(x,0,sizeof(x)); copy(rr,rr+50,r); backtrack(1); return
min ; } void
backtrack( int
t) { if(t > n ) compute(); else
{ for
(int
j =t ; j<= n ; j++ ) { swap(r[t],r[j]); float
centerx = center(t); if(centerx+r[t]+r[1] < min ){//below bound
x[t] = centerx ; backtrack(t+1); } swap(r[t],r[j]); } } } float
center(int
t ) { float
temp = 0 ; for
( int
j =1 ; j<t ; j++ ) { float
valuex =(float)(x[j]+2.0*sqrt(r[t]*r[j])); if(valuex>temp) temp = valuex; } return
temp; } void
compute() { float
low = 0 ; float
high = 0 ; for
( int
i = 1 ;i <=n ;i++) { if(x[i]-r[i]<low) low = x[i] - r[i]; if(x[i]+r[i]>high) high = x[i] + r[i]; } if(high - low < min ) min = high - low ; }};int
main(){ int
nn ; int
TT ; int
j =1 ; float
rr[50]; Circles cs ; cin>>TT; while(TT>0) { cin>>nn ; int
i = 1 ; while(i<=nn) { cin>>rr[i]; i++; } cs.circlePerm( nn , rr); printf("Case %d: %0.2f\n",j,cs.min); j++; TT--; } return
0 ;}
作者：laohan_ 发表于2012-12-31 23:57:15 原文链接
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