hdu 2122 Ice_cream’s world III

#include <iostream>
#include<stdio.h>
#include<algorithm>
using namespace std;
typedef struct{
int from,to,c;
}road;
road r[10000010];
int fa[1010];
int count;

int cmp(const void *a,const void *b){
return (((road *)a)->c > ((road *)b)->c)?1:-1;
}

int find(int a )
{
return fa[a]==a?a:fa[a]=find(fa[a]);
}

int main()
{
int ans,n,m,i,j;

while( scanf("%d %d",&n,&m)!=EOF){
int sum=0;
int ok=0;
ans=0;
for(i=0;i<n;i++)
fa[i]=i;
for(i=0;i<m;i++){
int temp_1,temp_2,c;
scanf("%d %d %d",&temp_1,&temp_2,&c);
r[sum].from=temp_1;
r[sum].to=temp_2;
r[sum++].c=c;
r[sum].from=temp_2;
r[sum].to=temp_1;
r[sum++].c=c;

}
qsort(r,sum,sizeof(road),cmp);
if(n==1)ok=1; //只有一个城市
else for(i=0;i<sum;i++){
int fa1=find(r[i].from);
int fa2=find(r[i].to);
if(fa1!=fa2){
fa[fa2]=fa1;
n--;
ans+=r[i].c;
if(n==1){
ok=1;
break;}
}
}
if(ok==1) printf("%d\n\n",ans);
else printf("impossible\n\n");
}
return 0;
}