求助！！最小生成树模板

#include<bits/stdc++.h>//Prim算法 
using namespace std;
const int Maxn=1e6+1;
int n,m,cnt,ans,tot,now=1;
int h[Maxn];
int dis[Maxn];
int vis[Maxn];
struct Skeleton
{
	int nxt,to,d;
}edg[Maxn<<1];

inline void read(int &num)
{
	int s=1,res=0;
	char in=getchar();
	while(!isdigit(in))
	{
		if(in=='-')
		{
			s=-1;
		}
		in=getchar();
	}
	while(isdigit(in))
	{
		res=(res<<1)+(res<<3)+in-'0';
		in=getchar();
	}
	num=res*s;
}
inline void build(int ogn,int dtn,int len)
{
	edg[++cnt].nxt=h[ogn];
	edg[cnt].to=dtn;
	edg[cnt].d=len;
	h[ogn]=cnt;
}
inline void Prim()
{
	memset(dis,0x7f,sizeof(dis));
	memset(vis,0,sizeof(vis));
	dis[1]=0;
	for(int i=h[1];i;i=edg[i].nxt)
	{
		int go=edg[i].to;
		dis[go]=min(dis[go],edg[i].d);
	}
	while(++tot<n)
	{
		int minn=0x7f;
		vis[now]=1;
		for(int i=1;i<=n;i++)
		{
			if(!vis[i]&&dis[i]<minn)
			{
				minn=dis[i];
				now=i;
			}
		}
		ans+=minn;
		for(int i=h[now];i;i=edg[i].nxt)
		{
			int go=edg[i].to;
			if(!vis[go]&&edg[i].d<dis[go])
			{
				dis[go]=edg[i].d;
			}
		}
	}
}
int main()
{
	//scanf("%d %d",&n,&m);
	read(n),read(m);
	for(int i=1;i<=m;i++)
	{
		int u,v,dist;
		//scanf("%d %d %d",&u,&v,&dist);
		read(u),read(v),read(dist);
		build(u,v,dist);
		build(v,u,dist);
	}
	Prim();
	printf("%d\n",ans);
	return 0;
}