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<cstdio>
#include<cstdlib>
#include<cmath>
#include<cstring>
#include<cctype>
#include<complex>
#include<iostream>
#include<sstream>
#include<algorithm>
#include<functional>
#include<vector>
#include<string>
#include<stack>
#include<queue>
#include<map>

using namespace std;
const int dx[] = {1,0,-1,0},dy[] = {0,1,0,-1};
#define INF 1e+8
#define rep(i,j) for(int i = 0; i < (j); i++)
#define reps(i,j,k) for(int i = j; i < k; i++)
typedef long long ll;
typedef unsigned long long ull;
int par[128];
int rank[128];
struct edge{
	int from,to,cst;
};
bool cmp(const edge& left, const edge& right){
	return left.cst < right.cst;
}
void init(int n){
	rep(i,n){
		par[i] = i;
		rank[i] = 0;
	}
}
int find(int x){
	if(par[x] == x)return x;
	else return par[x] = find(par[x]);
}
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[y] = x;
		if(rank[x] == rank[y])rank[x]++;
	}
}
bool same(int x,int y){
	return find(x) == find(y);
}
edge Data[128];
int main(){
	int n,m;
	while(scanf("%d%d",&n,&m),n|m){
		rep(i,m){
			scanf("%d%d%d",&Data[i].from,&Data[i].to,&Data[i].cst);
		}
		sort(Data,Data+m,cmp);
		init(n);
		int ans = 0;
		rep(i,m){
			edge next = Data[i];
			if(!same(next.from, next.to)){
				unite(next.from,next.to);
				ans += next.cst;
			}
		}
		printf("%d\n",ans);
	}
	return 0;
}

C++: #include <iostream>
#include <vector>
#include <queue>
#define INF (1e9)
#define cost first
#define node second
using namespace std;
typedef pair <int, int> P;
int n,m;
vector<P> G[101];

int prim(){
  int res = 0;
  bool visited[101]={};
  int D[101];
  for(int i=0;i<n;i++) D[i] = INF;
  priority_queue <P, vector<P>, greater<P> > Q;
  Q.push(P(0,0));
  while(!Q.empty()){
    P t = Q.top(); Q.pop();
    if(visited[t.node]) continue;
    visited[t.node] = true;
    res += t.cost;
    for(int i=0;i<G[t.node].size();i++){
      int nnode = G[t.node][i].node;
      int ncost = G[t.node][i].cost;
      if(D[nnode] > ncost) Q.push(P(ncost,nnode)),D[nnode]=ncost;
    }
  }
  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;
      G[a].push_back((P){c,b});
      G[b].push_back((P){c,a});
    }
    cout << prim()<<endl;
  }
  return 0;
}

C++: #include <iostream>
#define rep(i,n) for(int i=0;i<n;i++)
//#define int long long
using namespace std;

#define INF 999999

int n, m;
int a, b, c;

int cost[100][100];
int mincost[100];
bool used[100];

void init()
{
	rep(i,100) rep(j,100)
	{
		cost[i][j] = INF;
	}
}

int prim()
{
	rep(i,n)
	{
		mincost[i] = INF;
		used[i] = false;
	}

	mincost[0] = 0;
	int res = 0;

	while (true)
	{
		int v = -1;
		rep(u,n)
		{
			if (!used[u] && (v == -1 || mincost[u] < mincost[v])) v = u;
		}

		if (v == -1) break;
		used[v] = true;
		res += mincost[v];

		rep(u,n)
		{
			mincost[u] = min(mincost[u], cost[v][u]);
		}
	}

	return res;
}

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

		init();

		rep(i,m)
		{
			cin >> a >> b >> c;
			cost[a][b] = c;
			cost[b][a] = c;
		}

		printf("%d?\n", prim());
	}
}

C++: // Stellar Performance of the Debunkey Family
#include<iostream>
#include<vector>
#include<set>
#include<climits>
using namespace std;

#define NONE 0

int prim(int n, vector< vector<int> >v)
{
  set<int>selected;
  set<int>::iterator it;
  int mincost,mini;
  int i;
  int ans=0;

  selected.insert(0);

  while(selected.size()!=n){
    mincost=INT_MAX;
    mini=NONE;

    for(it=selected.begin();it!=selected.end();it++){
      for(i=0;i<n;i++){
	if(selected.find(i)!=selected.end())continue;
	if(v[*it][i]==NONE)continue;
	if(v[*it][i]>=mincost)continue;
	mincost=v[*it][i];
	mini=i;
      }
    }

    if(mini==NONE)break;
    selected.insert(mini);
    ans+=mincost;
  }

  return ans;
}

int main()
{
  int n,m,a,b,cost;
  int i;
  while(cin>>n>>m,n|m){
    vector< vector<int> >v(n,vector<int>(n,NONE));
    for(i=0;i<m;i++){
      cin>>a>>b>>cost;
      v[a][b]=v[b][a]=cost;
    }
    cout<<prim(n,v)<<endl;
  }
}

C++: #include <iostream>
#include <cmath>
#include <algorithm>
using namespace std;
int P[10010];
int N, M, A[10010], B[10010], COST[10010];
pair<int,int> bridge[10010];

void init(int N) {
	for (int i=0; i<N; ++i) { P[i] = i; }
}

int root(int a) {
	if (P[a] == a) return a;
	return (P[a] = root(P[a]));
}

bool is_same_set(int a, int b) {
	return root(a) == root(b);
}

void unite(int a, int b) {
	P[root(a)] = root(b);
}

int main() {
	
	while(cin >> N >> M) {
		int costs=0;
		if (N == 0 && M == 0) { break; }
		init(N);
		
		for (int i=0; i<M; i++) {
			cin >> A[i] >> B[i] >> COST[i];
			bridge[i].first = COST[i];
			bridge[i].second = i;
		}
		sort(bridge,bridge+M);
		
		for (int i=0; i<M; i++) {
			int cost = bridge[i].first;
			int machiID = bridge[i].second;
			if (!is_same_set(A[machiID], B[machiID])) {
				unite(A[machiID],B[machiID]);
				costs+=cost;
			}
		}
		cout << costs << endl;
	}
	return 0;
}