heap+prim

#include<cstdio>
#include<cstring>
using namespace std;


struct node
{
int num;
int dis;
node(int n,int d):num(n),dis(d){}
node(){}
};


int n;


node h[500000];


void insert(node nd,int& len)
{
len++;
h[len]=nd;
int loc=len;
while(loc>1)
{
if(h[loc].dis<h[loc>>1].dis)
{
node nt=h[loc];
h[loc]=h[loc>>1];
h[loc>>1]=nt;


loc>>=1;
}
else
{
break;
}
}
}


void heapfi(int loc,int len)
{
int min=loc;
int left=(loc<<1);
int right=left+1;


if(left<=len&&h[left].dis<h[min].dis)
{
min=left;
}
if(right<=len&&h[right].dis<h[min].dis)
{
min=right;
}
if(min!=loc)
{
node nt=h[loc];
h[loc]=h[min];
h[min]=nt;


heapfi(min,len);
}
}


node get(int&len)
{
node ret=h[1];
h[1]=h[len];
len--;
heapfi(1,len);
return ret;
}


int head[102];
int next[20005];
int point[20005];
int weight[20005];


int prim()
{
int ret=0;
int len=0;
bool fl[102]={0};
int low[102];
memset(low,0x1f,sizeof(low));
low[1]=0;
insert(node(1,0),len);
int cnt=0;
while(cnt<n&&len>0)
{
node nt=get(len);
if(fl[nt.num])continue;
fl[nt.num]=1;
ret+=nt.dis;
cnt++;
for(int e=head[nt.num];e!=-1;e=next[e])
{
if(low[point[e]]>weight[e])
{
low[point[e]]=weight[e];
insert(node(point[e],weight[e]),len);
}
}
}
return ret;
}


int main()
{
while(scanf("%d",&n),n)
{
memset(head,-1,sizeof(head));
memset(point,-1,sizeof(point));
memset(next,-1,sizeof(next));
int ec=n*(n-1)/2;
for(int i=1;i<=ec;i++)
{
int u,v,w;
scanf("%d%d%d",&u,&v,&w);
next[i]=head[u];
point[i]=v;
weight[i]=w;
head[u]=i;


next[i+ec]=head[v];
point[i+ec]=u;
weight[i+ec]=w;
head[v]=i+ec;
}
printf("%d\n",prim());
}
return 0;
}