kruskal算法。

#include
     
      #include
      
       #include
       
        #include
        
         using namespace std;const int maxn = 1000 + 10;const int maxm = 2000000 + 10;struct Point {    int x,y;} a[maxn];struct Edge {    int u,v,w;} g[maxm];int n,k,res,eid;int f[maxn];int find(int x) {    return f[x]==x?x:f[x]=find(f[x]);}int sqr(int x) {    return x*x;}int foo(Point a,Point b) {    return sqr(a.x-b.x)+sqr(a.y-b.y);    }void addedge(int a,int b,int c) {    ++eid; g[eid].u=a; g[eid].v=b; g[eid].w=c;    }bool cmp(Edge a,Edge b) {    return a.w
         
          k) {                f[ru]=rv;                n--;                }            else break;        }    }    printf("%.2lf\n",sqrt(g[res].w));    return 0;    }