usaco Chapter 3 section 3.1 Agri-Net

 /*
ID: niepeng1
LANG: C++
TASK:agrinet
*/

#include <iostream>
#include <algorithm>
#include <functional>
#include <vector>

using namespace std;

#define Max1 101
int map[Max1][Max1];
struct Node{
 int fro;
 int to;
 int val;
};
Node edge[Max1*Max1];
int cond[Max1];
int num,knum;
int total=0;
int cmp(const Node & a,const Node & b){return a.val>b.val;}

void Krustal()
{
 int i,k,j;
 int start=0,tem;
 for(k=0;k<num-1;k++){
  make_heap(edge+start,edge+knum,cmp);
  for(i=start;i<knum;i++){
   if( cond[edge[i].fro] != cond[edge[i].to] || (cond[edge[i].fro]==-1 && cond[edge[i].to]==-1))
    break;
  }
  total+=edge[i].val;
  if(edge[i].fro > edge[i].to)//fro 大 将被覆盖
  {
   tem=cond[edge[i].fro];
   if(cond[edge[i].to]==-1)
    cond[edge[i].to]=edge[i].to;
   cond[edge[i].fro]=cond[edge[i].to];
   if(tem != -1)
    for(j=0;j<num;j++)
    {
     if(cond[j] == tem)
      cond[j]=cond[edge[i].to];
    }
  }
  else
  {
   tem=cond[edge[i].to];//to是较大的
   if(cond[edge[i].fro]==-1)
    cond[edge[i].fro]=edge[i].fro;
   cond[edge[i].to]=cond[edge[i].fro];
   if(tem != -1)
    for(j=0;j<num;j++)
    {
     if(cond[j]==tem)
      cond[j]=cond[edge[i].fro];
    }
  }
  start=i+1;
 }
}

int main()
{
 FILE *in,*out;
 int i,j,tem;
 in=fopen("agrinet.in","r");
 out=fopen("agrinet.out","w");

 knum=0;
 fscanf(in,"%d",&num);
 for(i=0;i<num;i++)
  for(j=0;j<num;j++){
   fscanf(in,"%d",&tem);
   map[i][j]=tem;
   if( tem!=0)
   {
    edge[knum].fro=i;
    edge[knum].to=j;
    edge[knum].val=tem;
    knum++;
   }
   cond[i]=-1;
  }
 Krustal();
 fprintf(out,"%d/n",total);
 
// for(i=0;i<k;i++)
//  cout<<edge[i].val<<' ';

 

 fclose(in);
 fclose(out);
 

 return 0;
}