3390: [Usaco2004 Dec]Bad Cowtractors牛的报复

#include<algorithm>
#include<iostream>
#include<cstdio>
using namespace std;
inline int read(){
int x=0,f=1;char ch=getchar();
while(ch<'0'||ch>'9'){if(ch=='-')f=-1;ch=getchar();}
while(ch>='0'&&ch<='9'){x=x*10+ch-'0';ch=getchar();}
return x*f;
}
struct edge{
int x,y,z;
}e[20001];
int n,m,cnt=1,ans,tot,fa[1001];
inline bool cmp(edge a,edge b){return a.z>b.z;}
int find(int x){return fa[x]==x?x:find(fa[x]);}
int main(){
n=read();m=read();
for(int i=1;i<=m;i++){
int x=read(),y=read(),z=read();
e[++tot]=(edge){x,y,z};
}
sort(e+1,e+tot+1,cmp);
for(int i=1;i<=n;i++)fa[i]=i;
for(int i=1;i<=tot;i++){
int p=find(e[i].x),q=find(e[i].y);
if(p!=q){ans+=e[i].z;cnt++;fa[p]=q;if(cnt==n){printf("%d",ans);return 0;}}
}
printf("-1");
return 0;
}