MST......

#include <iostream>
#include <cstdio>
#include <cstdlib>
#include <algorithm>
using namespace std;
struct jc{
int fm,to,dist;
}e[3000];
int f[3000],g[1001][1001],n,ans=0,m,maxint=1073741824;
int find(int x) {
if (f[x]!=x) f[x]=find(f[x]);
return f[x];
}
//路径压缩
void merge(int x,int y){
int xx=find(x);
int yy=find(y);
f[xx]=yy;
}

bool cmp(jc a,jc b){
return a.dist<b.dist;
}
//cmp
int main(){
scanf("%d%d",&n,&m);
for(int i=1;i<=m;i++)
scanf("%d%d%d",&e[i].fm,&e[i].to,&e[i].dist);
sort(e+1,e+m+1,cmp);
for(int i=1;i<=n;i++) f[i]=i;
int rst=n;//用于记录加入的边
for(int i=1;i<=m && rst>1;i++)
{
int x=e[i].fm,y=e[i].to;
if(find(x)!=find(y))//查
{
merge(x,y);//并
rst--;
ans+=e[i].dist;
}
}
printf("%d",ans);
return 0;
}