Go: // Find the minimum spanning tree by the Kruskal algorithm
// -------------------------------------------------------
// Kruskal(G):
//     A = ∅
//     foreach v ∈ G.V:
//        MAKE-SET(v)
//     foreach (u, v) in G.E ordered by weight(u, v), increasing:
//         if FIND-SET(u) ≠ FIND-SET(v):
//             A = A ∪ {(u, v)}
//             UNION(u, v)
//     return A
//
// Ref: https://en.wikipedia.org/wiki/Kruskal%27s_algorithm

package main

import (
	"bufio"
	"os"
	"sort"
	"strconv"
	"strings"
	"fmt"
	)

var scanner = bufio.NewScanner(os.Stdin)
var (
	matrix [][]int
)

type Edge struct {
	a, b, cost, added int
}
type ByCost []Edge

var edges ByCost

func (a ByCost) Len() int           { return len(a) }
func (a ByCost) Swap(i, j int)      { a[i], a[j] = a[j], a[i] }
func (a ByCost) Less(i, j int) bool { return a[i].cost < a[j].cost }

func main() {
	for scanner.Scan() {
		buf := strings.Split(scanner.Text(), " ")
		n, _ := strconv.Atoi(buf[0])
		m, _ := strconv.Atoi(buf[1])
		if n == 0 && m == 0 {
			break
		}
		matrix = make([][]int, n)
		for i := range matrix {
			matrix[i] = make([]int, n)
		}
		for i := 0; i < m; i++ {
			scanner.Scan()
			buf_ := strings.Split(scanner.Text(), " ")
			a, _ := strconv.Atoi(buf_[0])
			b, _ := strconv.Atoi(buf_[1])
			cost, _ := strconv.Atoi(buf_[2])
			matrix[a][b] = cost
			matrix[b][a] = cost
		}
		sum := Kruskal(n)
		fmt.Println(sum)
		if len(edges) > 0 {
			edges = []Edge{}
		}
	}
}

func Kruskal_func(size, edge_num int) int {
	for i := 0; i < size; i++ {
		for j := 0; j < size; j++ {
			if matrix[i][j] > 0 {
				tmp := Edge{i, j, matrix[i][j], 0}
				edges = append(edges, tmp)
			}
		}
	}
	sort.Sort(ByCost(edges))
	UF_Init(edge_num)
	for i := 0; i < edge_num; i++ {
		a := edges[i].a
		b := edges[i].b
		if UF_Find(a) != UF_Find(b) {
			edges[i].added = 1
			UF_Union(UF_Find(a), UF_Find(b))
		}
	}
	sum := 0
	for i := 0; i < edge_num; i++ {
		if edges[i].added != 0 {
			// log.Printf("edge(%d,%d) is added\n", edges[i].a, edges[i].b)
			sum += edges[i].cost
		}
	}
	return sum
}

func Kruskal(size int) int {
	edge_num := 0
	for i := 0; i < size; i++ {
		for j := 0; j < size; j++ {
			if matrix[i][j] > 0 {
				edge_num++
			}
		}
	}
	return Kruskal_func(size, edge_num)
}

/*** Union-Find functions ***/
var UF_Parent []int
var UF_Rank []int

func UF_Init(n int) {
	UF_Parent = make([]int, n)
	UF_Rank = make([]int, n)
	for i := 0; i < n; i++ {
		UF_Parent[i] = i
		UF_Rank[i] = 0
	}
}
func UF_Union(a, b int) {
	if UF_Rank[a] < UF_Rank[b] {
		UF_Parent[a] = b
	} else {
		UF_Parent[b] = a
	}
	if UF_Rank[a] == UF_Rank[b] {
		UF_Rank[a]++
	}
}
func UF_Find(a int) int {
	if UF_Parent[a] == a {
		return a
	}
	return UF_Find(UF_Parent[a])
}
/*** Union-Find functions ***/

C++: #include <iostream>
#include <string>
#include <math.h>
#include <algorithm>
#include <climits>
#include <vector>

using namespace std;

typedef vector< int > VI;
typedef vector< VI > VVI;

struct edge{ int from, to, cost; };

#define MAX_N 101
#define MAX_E 1000

int par[MAX_N];
int Rank[MAX_N];
edge map[MAX_E];

// nで初期化
void init( int n ) {
	for(int i = 0; i < n; i++) {
		par[i] = i;
		Rank[i] = 0;
	}
}

// 木の根を求める
int find( int x ) {
	if(par[x] == x) {
		return x;
	} else {
		return par[x] = find(par[x]);
	}
}

// xとyの属する集合を合併
void unite( int x, int y ){
	x = find(x);
	y = find(y);

	if( x == y ) {
		return;
	}

	if( Rank[x] < Rank[y] ) {
		par[x] = y;
	} else {
		par[x] = y;
		if( Rank[x] == Rank[y] ) {
			Rank[x]++;
		}
	}
}

// xとyが同じ集合に属するか否か
bool same( int x, int y ) {
	return find(x) == find(y);
}


bool comp( const edge& e1, const edge& e2) {
	return e1.cost < e2.cost;
}

int main() {
	int n, m;

	while( true ){
		cin >> n >> m;
		if(n == 0 && m == 0) {
			break;
		}

		int a, b, c;
		for(int i = 0; i < m; i++) {
			cin >> a >> b >> c;
			map[i].from = a;
			map[i].to = b;
			map[i].cost = c;
		}

		sort(map, map + m, comp);
		init(n);
		int res = 0;
		for(int i = 0; i < m; i++) {
			edge e = map[i];
			if(!same(e.from, e.to)) {
				unite(e.from, e.to);
				res += e.cost;
			}
		}

		cout << res << endl;
	}
}

C++: #include<bits/stdc++.h>
using namespace std;
typedef long long int ll;
typedef pair<ll,ll> mp;
#define inf 1e9


int main(){
    while(1){
	int n,m;
	cin>>n>>m;
	if(n==0)break;
	vector<vector<mp> > g(n);
	for(int i=0;i<m;i++){
		int a,b,c;
		cin>>a>>b>>c;
		g[a].push_back(mp(c,b));
		g[b].push_back(mp(c,a));
	}
	priority_queue<mp,vector<mp>,greater<mp> > q;
	for(int i=0;i<g[0].size();i++)q.push(g[0][i]);
	int sum = 0;
	vector<bool> used(n,false);
	used[0] = true;
	//cout<<"ok"<<endl;
	while(!q.empty()){
		mp now = q.top();
		q.pop();
		int nn = now.second;
		int cost = now.first;
		if(used[nn])continue;
	//	cout<<nn<<' '<<cost<<endl;
		used[nn] = true;
		sum+=cost;
		for(int i=0;i<g[nn].size();i++){
		    	if(used[g[nn][i].second])continue;
			q.push(g[nn][i]);
		}

	}
	cout<<sum<<endl;
	}
	return 0;
}

C++: #include<iostream>
#include<cstring>
#include<vector>
#include<queue>
using namespace std;
int main()
{
  int n,m;
  for(;cin>>n>>m,n;)
    {
      int edge[n][n];
      memset(edge,-1,sizeof(edge));
      for(int i=0;i<m;i++)
	{
	  int a,b,cost;
	  cin>>a>>b>>cost;
	  edge[a][b]=cost;
	  edge[b][a]=cost;
	}
      bool closed[n];
      int cnt=n-1;
      int ans=0;
      memset(closed,false,sizeof(closed));
      closed[0]=true;
      priority_queue<pair<int,int>, vector<pair<int,int> > ,greater<pair<int,int> > > qu;
      for(int i=0;i<n;i++)
	{
	  if(edge[0][i]!=-1)
	    qu.push(make_pair(i,edge[0][i]));
	}
      while(true)
	{
	  int pos=qu.top().first;
	  int cost=qu.top().second;
	  qu.pop();
	  if(closed[pos])
	    continue;
	  closed[pos]=true;
	  ans+=cost;
	  cnt--;
	  if(cnt<=0)
	    break;
	  for(int i=0;i<n;i++)
	    {
	      if(!closed[i]&&edge[pos][i]!=-1)
		qu.push(make_pair(i,edge[pos][i]));
	    }
	}
      cout<<ans<<endl;
    }

}

C++: //kruskal tree
#include <iostream>
#include <algorithm>
using namespace std;
#define M 999
int parent[M],a[M],b[M];
pair<int,int>node[M];
int root(int a){
	return parent[a]==a?a:parent[a]=root(parent[a]);
}
int unite(int a,int b){
	int x=root(a),y=root(b);
	if(x==y)return 0;
	parent[x]=y;
	return 1;
}
int main(){
	int i,s,n,m;
	for(;cin>>n>>m,n;cout<<s<<endl){
		for(i=0;i<m;i++)cin>>a[i]>>b[i]>>node[i].first,node[i].second=i;
		sort(node,node+m);
		for(i=0;i<n;i++)parent[i]=i;
		for(s=i=0;i<m;i++)if(unite(a[node[i].second],b[node[i].second]))s+=node[i].first;
	}
}

C++: #include <iostream>
#include <map>
#include <vector>
#include <algorithm>
#include <numeric>

using namespace std;

int data[101][101];

int prim( int n )
{
	vector<int> key( n, numeric_limits<int>::max() );
	key[0] = 0;
	vector<int> pq;
	vector<bool> inQueue( n, true );
	for( int i = 0;i < n;i++ ){
		pq.push_back( key[i] );
	}

	while( !pq.empty() ){
		vector<int>::iterator it = min_element( pq.begin(), pq.end() );
		int u = distance( pq.begin(), it );
		pq.erase( it );
		inQueue[u] = false;

		for( int i = 0;i < n;i++ ){
			if( data[u][i] ){
				if( inQueue[i] ){
					int w = data[u][i];
					if( w < key[i] ){
						key[i] = w;
						pq[i] = w;
					}
				}
			}
		}
	}

	int answer = 0;
	for( int i = 0;i < n;i++ ){
		answer += key[i];
	}

	return answer;
}

int main(int argc, char const* argv[])
{
	int n,m;
	int a,b,cost;

	while( cin >> n >> m && n != 0 ){
		for( int i = 0;i < 101;i++ ){
			for( int j = 0;j < 101;j++ ){
				data[i][j] = 0;
			}
		}
		for( int i = 0;i < m;i++ ){
			cin >> a >> b >> cost;
			data[a][b] = cost;
			data[b][a] = cost;
		}

		int answer = prim( n );
		cout << answer << endl;
	}

	return 0;
}