1 /*AC 19ms*/ 2 #include<stdio.h> 3 #include<stdlib.h> 4 #include<math.h> 5 #include<string.h> 6 #include<algorithm> 7 #define INF 1000000 8 const int maxn=500+5; 9 double lowdist[maxn];10 bool in[maxn];11 int x[maxn],y[maxn];12 double dist(int x1,int y1,int x2,int y2)13 {14     return sqrt((x1-x2)*(x1-x2)+(y1-y2)*(y1-y2));15 }16 void prim(int n)17 {18     lowdist[1]=0;19     for(int i=2;i<=n;i++){20         lowdist[i]=dist(x[1],y[1],x[i],y[i]);21         in[i]=false;22     }23     in[1]=true;24     for(int i=1;i<n;i++){25         double mindist=INF;26         int j=1;27         for(int k=1;k<=n;k++)28         if(mindist>lowdist[k] && !in[k]){29             mindist=lowdist[k];30             j=k;31         }32         in[j]=true;33         for(int k=1;k<=n;k++){34             double temp=dist(x[j],y[j],x[k],y[k]);35             if(lowdist[k]>temp && !in[k])36                 lowdist[k]=temp;37         }38     }39 }40 int main()41 {42     int t,m,n;43     scanf("%d",&t);44     while(t--){45         scanf("%d%d",&m,&n);46         for(int i=1;i<=n;i++)47             scanf("%d%d",&x[i],&y[i]);48         prim(n);49         std::sort(lowdist+1,lowdist+1+n);50         printf("%0.2f\n",lowdist[n-m+1]);51     }52     return 0;53 }