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 "bits/stdc++.h"
using namespace std;
using ll = long long; using ull = unsigned long long;
using vb = vector<bool>;
using vi = vector<int>; using vvi = vector<vector<int>>;
using vl = vector<ll>; using vvl = vector<vector<ll>>;
using pii = pair<int,int>; using pll = pair<ll,ll>;
#define FOR(i,a,b) for(ll i = (a); i < (ll)(b); i++)
#define REP(i,n) FOR(i,0,n)
#define ALL(obj) (obj).begin(), (obj).end()
#define rALL(obj) (obj).rbegin(), (obj).rend()
#define eb(val) emplace_back(val)
const double PI = acos(-1);
const double EPS = 1e-10;
const ll MOD = 1e9+7;
//#define int ll
void cioacc(){//accelerate cin/cout
  cin.tie(0);
  ios::sync_with_stdio(false);
}
struct edge{
  int to,wt,from;
  bool operator<(edge right){
    return wt < right.wt;
  }
};
using ve = vector<edge>;
using vve = vector<ve>;
struct union_find{//rank,経路圧縮で高速化
  vector<long long> data;//そのノードがrootであれば-（集合のサイズ）を表し、そうでなければ親ノードidを示す。
  union_find(long long size):data(size,-1){}//コンストラクタ,size個のノードを作成し、-1で初期化
  long long root(long long a){//根を探す,経路圧縮
    return data[a] < 0 ? a : data[a]=root(data[a]);
  }
  bool find(long long a,long long b){//a,bが同じ集合に属するか調べる
    return root(a) == root(b);
  }
  bool unite(long long a,long long b){//小さい方の木の根に大きい方の根を上書きする
    a = root(a),b = root(b);
    if(a==b) return false;//根が同じなら終了,uniteが失敗したことを出力
    if(data[a]<data[b]) swap(a,b); //集合サイズの大きい方の根に低い方の根をつける
    data[a] += data[b];//集合サイズを統合
    data[a] = b;//yの親にxをつける
    return true;//unite成功を出力
  }
  long long size(long long a){//aが属する集合のサイズを出力
    return -data[root(a)];
  }
};
int kruskal(int sz,ve &edges){
  sort(rALL(edges));
  union_find uf(sz);
  int res = 0;
  while(!edges.empty()){
    edge &e = edges.back();
    edges.pop_back();
    if(!uf.unite(e.to,e.from)) continue;
    res += e.wt;
  }
  return res;
}
signed main(){
  int v,e;
  while(cin >> v >> e,v){
    ve edges(e);
    REP(i,e){
      int nd1,nd2,wt;
      cin >> nd1 >> nd2 >> wt;
      edges[i]=(edge){nd1,wt,nd2};
    }
    cout << kruskal(v,edges) << endl;
  }
}

C++: #include <cstdio>
#include <algorithm>

using namespace std;

//disjoint-set
int parent[100];

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

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

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

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

//graph
class Edge{
public:
  int cost,a,b;
  Edge(int c=0,int d=0,int e=0):cost(c),a(d),b(e){}
  bool operator< (const Edge& o) const {
    return cost < o.cost;
  }
};

//main
int n,m;
Edge graph[100];

int main(){
  while(scanf("%d %d",&n,&m),n){
    for(int i=0; i<m; i++){
      int a,b,cost;
      scanf("%d %d %d",&a,&b,&cost);
      graph[i] = Edge(cost,a,b);
    }

    sort(graph,graph+m);

    int answer=0;
    init(n);

    for(int i=0; i<m; i++){
      Edge e = graph[i];
      if(!same_set_p(e.a,e.b)){
	answer += e.cost;
	unite(e.a,e.b);
      }
    }

    printf("%d\n",answer);
  }
}

C++: #include <iostream>
#include <vector>
#include <iostream>
#include <string>
#include <cstdio>
#include <algorithm>
using namespace std;
int par[104];
int ran[105];
void init(int n) {
	for (int i = 0; i<n; i++) {
		par[i] = i;
		ran[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 (ran[x]<ran[y]) {
		par[x] = y;
	}
	else {
		par[y] = x;
		if (ran[x] == ran[y]) ran[x]++;
	}
}
bool same(int x, int y) {
	return find(x) == find(y);
}
struct edge { int s, t, cost; };
bool comp(const edge& e1,const edge& e2) {
	return e1.cost < e2.cost;
}
int main()
{
	int n, m;
	while (cin >> n >> m, n != 0) {
		init(n);
		edge b[10008];
		int x, y, z;
		for (int i = 0; i < m; i++) {
			cin >> x >> y >> z;
			b[i].s = x;
			b[i].t = y;
			b[i].cost = z;
		}
		int ans = 0;
		sort(b, b + m, comp);
		for (int i = 0; i < m; i++) {
			edge now = b[i];
			if (!same(now.s, now.t)) {
				unite(now.s, now.t);
				ans += now.cost;
			}
		}cout << ans<<endl;
	}
	return 0;
}