csu 1541: There is No Alternative（Kruskal 最小生成树）

#include<cstdio>
#include<cstring>
#include<iostream>
#include<algorithm>
using namespace std;
const int MAXN=1000000+5;
struct road
{
  int f,t;
  int w;
};
road vil[MAXN];
int fa[1000+5];
int target[MAXN];
int n,m;
int mark,coun;
int cmp(road a,road b)
{
  return a.w<b.w;
}
int findfa(int x)
{
  return fa[x]==x?x:fa[x]=findfa(fa[x]);
}
int kruskal(int flag)
{
  int res=0;
  for(int i=1;i<=n;i++) fa[i]=i;//!!!!!!!这里错了，应该是对村庄一开始是以自己为根不是路！
  for(int i=0;i<m;i++)
  {
    if(i==flag) continue;
    int x=findfa(vil[i].f);
    int y=findfa(vil[i].t);
    if(x!=y)
    {
      if(mark==0)
      {
        target[coun++]=i;
      }
      fa[x]=y;
      res+=vil[i].w;
    }
  }
  return res;

}
int main()
{
  int i,j,k;
  int cnt,worth,temp;
    scanf("%d%d",&n,&m);
    cnt=0;
    worth=0;
    mark=0;
    coun=0;
    for(i=0;i<m;i++)
    {
      scanf("%d%d%d",&vil[i].f,&vil[i].t,&vil[i].w);
    }
    sort(vil,vil+m,cmp);
    int ans=kruskal(-1);
    //printf("%d
",ans);
    mark=1;
    for(i=0;i<coun;i++)
    {
      int temp=kruskal(target[i]);
      //printf("temp=%d i=%d
",temp,vil[target[i]].w);
      if(temp!=ans) {cnt++;worth+=vil[target[i]].w;}
    }
    printf("%d %d
",cnt,worth);
  return 0;
}