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 <iomanip>
#include <sstream>
#include <cstdio>
#include <cstdlib>
#include <cmath>
#include <cstring>
#include <climits>
#include <cfloat>
#include <string>
#include <vector>
#include <stack>
#include <queue>
#include <set>
#include <map>
#include <bitset>
#include <algorithm>
#include <functional>
#include <utility>
#include <numeric>

using namespace std;

typedef unsigned int UI;
typedef long long LL;
typedef unsigned long long ULL;
typedef vector<int> VI;
typedef vector<VI> VVI;
typedef vector<string> VS;
typedef pair<int,int> PII;
typedef istringstream ISS;
typedef ostringstream OSS;

#define REP( i, m, n ) for ( int i = (int)( m ); i < (int)( n ); ++i )
#define EACH( v, c ) for ( auto &v : c )

#define ITER( c ) __typeof( (c).begin() )
#define IREP( c, it ) for ( ITER(c) it = c.begin(); it != c.end(); ++it )
#define ALL( c ) (c).begin(), (c).end()

#define PB( n ) push_back( n )
#define MP( a, b ) make_pair( ( a ), ( b ) )
#define EXIST( c, e ) ( (c).find( e ) != (c).end() )

#define fst first
#define snd second

#define DUMP( x ) cerr << #x << " = " << ( x ) << endl
#define DEBUG( x ) cerr << __FILE__ << ":" << __LINE__ << ": " << #x << " = " << ( x ) << endl

int main()
{
	cin.tie( 0 );
	ios::sync_with_stdio( false );

	while ( true )
	{
		int n, m;
		cin >> n >> m;

		if ( !( n | m ) )
		{
			break;
		}

		vector< vector< PII > > G( n );

		REP( i, 0, m )
		{
			int a, b, c;
			cin >> a >> b >> c;

			G[a].PB( MP( b, c ) );
			G[b].PB( MP( a, c ) );
		}

		priority_queue< PII, vector< PII >, greater< PII > > que;
		que.push( MP( 0, 0 ) );

		vector< bool > used( n, false );

		int res = 0;

		while ( !que.empty() )
		{
			auto cur = que.top();
			que.pop();

			if ( used[ cur.snd ] )
			{
				continue;
			}

			used[ cur.snd ] = true;
			res += cur.fst;

			EACH( e, G[ cur.snd ] )
			{
				auto next = MP( e.snd, e.fst );

				que.push( next );
			}
		}

		cout << res << endl;
	}

	return 0;
}

C++: #include <iostream>
#include <set>
#include <algorithm>

using namespace std;

int n, m;
vector< set< pair<int, int> > > cost(100,set< pair<int,int> >());

int prim()
{
	int res=0;
	set<int> v;
	v.insert(0);
	while(v.size()<n)
	{
		pair<int, int> mini(100000007, -1);
		for(set<int>::iterator it=v.begin();it!=v.end();it++)
		{
			for(set<  pair<int, int> >::iterator it2=cost[*it].begin();it2!=cost[*it].end();it2++)
				if(v.find((*it2).second)==v.end())
				{
					if(mini.first>(*it2).first)
						mini=(*it2);
					break;
				}
		}
		v.insert(mini.second);
		res+=mini.first;
	}
	return res;
}

int main()
{
	while(1)
	{
		cin >> n >> m;
		if(n==0&&m==0) break;
		for(int i=0;i<m;i++)
		{
			int a, b, c;
			cin >> a >> b >> c;
			cost[a].insert(pair<int, int>(c, b));
			cost[b].insert(pair<int, int>(c, a));
		}
		cout << prim() << endl;
		for(int i=0;i<m;i++)
			cost[i].clear();
	}
	return 0;
}

C++: #include<iostream>
#include<algorithm>
using namespace std;
typedef struct{
	int u,v,co;
}wa;
bool com(const wa& a,const wa& b){
	return a.co<b.co;
}
wa way[1000];
int pa[1000];
int find(int t){
	if(pa[t]==t)
	return t;
	else return find(pa[t]);
}
void uni(int s,int t){
	s=find(s);
	t=find(t);
	pa[s]=t;
}
int same(int x,int y){
	return find(x)==find(y);
}
int main(){
	int n,m,sum;
	while(cin>>n>>m,n||m){
		sum=0;
		for(int i=0;i<m;i++)
			cin>>way[i].v>>way[i].u>>way[i].co;
		for(int i=0;i<n;i++)
			pa[i]=i;
		sort(way,way+m,com);
		for(int i=0;i<m;i++){
			if(!same(way[i].u,way[i].v)){
				uni(way[i].u,way[i].v);
				sum+=way[i].co;
			}
		}
		cout<<sum<<endl;
	}
	return 0;
}

C++: #include <bits/stdc++.h>
using namespace std;
#define FOR(i,k,n) for(int i = (k); i < (n); i++)
#define REP(i,n) FOR(i,0,n)
#define INF 114514810
#define MOD 1000000007
#define ALL(a) (a).begin(),(a).end()
#define pb(x) push_back(x)
#define ms(m,v) memset(m,v,sizeof(m))
#define D10  fixed<<setprecision(10) 
typedef vector<int> vi;
typedef vector<string> vs;
typedef pair<int, int> P;
typedef long long ll;
struct edge{ int from, to, cost; };

///**********************************///
///**********Union-Find Tree*********///
///**********************************///
const int N = 1000;
int par[N]; int hukasa[N];

int find(int x)
{
	if (par[x] == x) return x;
	else par[x] = find(par[x]);
}

void unite(int x, int y)
{
	x = find(x); y = find(y);
	if (x == y) return;
	if (hukasa[x] < hukasa[y]) par[x] = y;
	else
	{
		par[y] = x;
		if (hukasa[x] == hukasa[y]) hukasa[x]++;
	}
}

int same(int x, int y)
{
	return find(x) == find(y);
}

void init_UFT(int n) //要素数nのUFTを初期化
{
	REP(i, n)
	{
		par[i] = i;
		hukasa[i] = 0;
	}
}

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

vector<edge> es;
int main()
{
	int n, m;
	while (cin >> n >> m, n)
	{
		init_UFT(n);
		es.clear();
		int a, b, c;
		REP(i, m)
		{
			cin >> a >> b >> c;
			edge e = { a, b, c };
			es.push_back(e);
		}
		sort(ALL(es), comp);
		int sum = 0;
		REP(i, es.size())
		{
			if (!same(es[i].from, es[i].to))
			{
				unite(es[i].from, es[i].to);
				sum += es[i].cost;
			}
		}
		cout << sum << endl;
	}

	return 0;
}