HDU 1875: 畅通工程再续

Posted 2020-10-07

///@author Sycamore
///@date 9/16/2017
///@link http://acm.hdu.edu.cn/showproblem.php?pid=1875
#include<bits/stdc++.h>
using namespace std;
const double eps=1e-7;
struct Edge
{
   int from,to;
   double length;
   friend bool operator<(const Edge &u,const Edge &v)
   {
      return u.length<v.length;
   }
}edge[5000];

int c,n=0,parent[100];
void AddEdges()
{
   cin>>c;
   vector<pair<int,int>>island(c);
   for(auto &e:island)cin>>e.first>>e.second;
   for(int i=0;i<c;i++)
      for(int j=i+1;j<c;j++)
      {
         double dist=hypot(island[i].first-island[j].first,island[i].second-island[j].second);
         if(dist>10-eps&&dist<1000+eps)
            edge[n++]=Edge{i,j,dist};
      }
}
int Find(int x)
{
   return parent[x]==-1?x:parent[x]=Find(parent[x]);
}
void Union(int x,int y)
{
   parent[Find(x)]=Find(y);
}
double Kruskal()
{
   double price=0;
   sort(edge,edge+n);
   fill(parent,parent+c,-1);
   int counter=0;
   for(int i=0;i<n;i++)
   {
      int u=Find(edge[i].from),v=Find(edge[i].to);
      if(u==v)continue;
      else
      {
         counter++;
         Union(u,v);
         price+=edge[i].length;
      }
   }
   if(counter<c-1)return -1;
   return price*100;
}
int main()
{
   ios::sync_with_stdio(false);
   cin.tie(0);
   int T;
   cin>>T;
   while(T--)
   {
      n=0;
      AddEdges();
      double result=Kruskal();
      if(result<0)
         cout<<"oh!\n";
      else cout<<fixed<<setprecision(1)<<result<<‘\n‘;
   }
   return 0;
}