1 #include<iostream>  2 #include<cmath>  3 #include<algorithm>  4 #include<cstdio>  5 using namespace std;  6 #define maxn 600  7 int par[maxn];  8 int pos;  9 int n,cnt,m; 10 double len; 11 double tt[maxn];//存选取的道路 12 struct node 13 { 14     int x; 15     int y; 16     double w; 17 }; 18 node e[maxn * (maxn - 1) / 2]; 19 int cmp(const node &a , const node &b) 20 { 21     return a.w < b.w; 22 }; 23 struct p 24 { 25     int x; 26     int y; 27 } po[maxn]; 28 void init() 29 { 30     for(int i = 0; i <= n+5; i++) 31         par[i] = i; 32     pos = 0; 33     len = 0.0; 34     cnt = 0; 35 } 36 int Find(int x) 37 { 38     int k,j,r; 39     r = x; 40     while(par[r] != r) 41         r = par[r]; 42     k = x; 43     while(k != r) 44     { 45         j = par[k]; 46         par[k] = r; 47         k = j; 48     } 49     return r; 50 } 51 int Merge(int x,int y) 52 { 53     int a = Find(x); 54     int b = Find(y); 55     if(a != b) 56     { 57         par[a] = par[b]; 58         return 1; 59     } 60     return 0; 61 } 62 void input() 63 { 64     int u,v; 65     for(int i = 1; i <= n; i++) 66         scanf("%d%d",&po[i].x,&po[i].y); 67 } 68  69 void make() 70 { 71     init(); 72     double dist; 73     for(int i = 1; i < n; i++) 74     { 75         for(int j = i + 1; j <= n; j++) 76         { 77             dist = (po[i].x - po[j].x) * (po[i].x - po[j].x) + (po[i].y - po[j].y) * (po[i].y - po[j].y); 78             e[pos].x = i; 79             e[pos].y = j; 80             e[pos].w = sqrt(dist); 81             pos++; 82         } 83     } 84     sort(e,e+pos,cmp); 85     for(int i = 0; i < pos; i++) 86     { 87         if(Merge(e[i].x,e[i].y)) 88         { 89             tt[cnt] = e[i].w; 90             cnt++; 91         } 92         if(cnt == n - 1)break; 93     } 94 } 95 int main() 96 { 97     freopen("input.txt","r",stdin); 98     int t; 99     scanf("%d",&t);100     while(t--)101     {102         scanf("%d%d",&m,&n);103         input();104         make();105         printf("%.2lf\n",tt[cnt - m]);106     }107 108     return 0;109 }