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 <vector>
#include <queue>
#include <algorithm>
#include <functional>

using namespace std;
typedef pair<int, int> P;
static const int INF = 9999999;
struct SEdge
{
	int To;
	int Cost;
};
int V, E;
vector<int> mincost;
vector< vector<SEdge> > Edge;
bool used[128];

int Prim()
{
	fill(used, used + V, false);
	fill(mincost.begin(), mincost.end(), INF);
	mincost[0] = 0;
	priority_queue<P, vector<P>, greater<P> > PQue;
	PQue.push(P(0, 0));
	int res = 0;
	while(!PQue.empty())
	{
		P p = PQue.top();
		PQue.pop();
		int v = p.second;
		if(mincost[v] < p.first || used[v])
		{
			continue;
		}
		used[v] = true;
		res += mincost[v];
		for(int i = 0; i < Edge[v].size(); ++i)
		{
			SEdge e = Edge[v][i];
			if(mincost[e.To] > e.Cost)
			{
				mincost[e.To] = e.Cost;
				PQue.push(P(mincost[e.To], e.To));
			}
		}
	}
	return(res);
}

void solve()
{
	while(cin >> V >> E, V || E)
	{
		mincost.clear();
		mincost.resize(V);
		for(int i = 0; i < Edge.size(); ++i)
		{
			Edge[i].clear();
		}
		Edge.clear();
		Edge.resize(V);
		for(int i = 0; i < E; ++i)
		{
			int From, To, Cost;
			cin >> From >> To >> Cost;
			SEdge e1, e2;
			e1.To = To;
			e2.To = From;
			e1.Cost = e2.Cost = Cost;
			Edge[From].push_back(e1);
			Edge[To].push_back(e2);
		}
		cout << Prim() << endl;
	}
}

int main()
{
	solve();
	return(0);
}

C++: #include <iostream>
#include <algorithm>
using namespace std;

const int INF = 1000000;
int main(){
	int n,m;
	while(cin >> n >> m){
		if(!n && !m)
			break;
		int bridge[101][101];
		int pre_vertex[101][101];
		int a,b,cost;
		for(int i=0;i<101;i++){
			for(int j=0;j<101;j++){
				if(i==j)
					bridge[i][j] = 0;
				else
					bridge[i][j] = INF;
				pre_vertex[i][j] = i;
			}
		}
		for(int i=0;i<m;i++){
			cin >> a >> b >> cost;
			if(bridge[a][b] > cost){
				bridge[a][b] = cost;
				bridge[b][a] = cost;
			}
		}
		//ツフツδ債イツド
		for(int k=0;k<n;k++){
			for(int i=0;i<n;i++){
				for(int j=0;j<n;j++){
					int dis = bridge[i][k]+bridge[k][j];
					if(dis < bridge[i][j]){
						bridge[i][j] = dis;
						pre_vertex[i][j] = pre_vertex[k][j];
					}	
				}
			}
		}
		int min = INF;
		for(int i=0;i<n;i++){
			int sum = 0;
			for(int j=0;j<n;j++){
				sum += bridge[i][j];
				sum -= bridge[i][pre_vertex[i][j]];
			}
			if(sum < min)
				min = sum;
		}
		cout << min << endl;
	}
	return 0;
}

C++: 
#include <iostream>
#include <algorithm>
using namespace std;

#define MAX_N 10000

int par[MAX_N];
int rank[MAX_N];

#define MAX_E 10000
struct edge { int u, v, cost; };
edge es[MAX_E];

int V, E;

void init_union_find(int n) {
  for(int i=0; i<n; i++) {
    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);
}

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

int kruskal() {
  sort(es, es + E, comp);
  init_union_find(V);
  int res = 0;
  for(int i=0; i<E; i++) {
    edge e = es[i];
    if(!same(e.u, e.v)) {
      unite(e.u, e.v);
      res += e.cost;
    }
  }
  return res;
}

int main() {

  while(cin >> V >> E && (V||E)) {
    E *= 2;
    for(int i=0; i<E; i+=2) {
      int a, b, c;
      cin >> a >> b >> c;
      es[i].u = a, es[i].v = b, es[i].cost = c;
      es[i].u = b, es[i].v = a, es[i].cost = c;
    }
    cout << kruskal() << endl;
  }
  
  return 0;
}

C++: #include <iostream>
#include <climits>
using namespace std;
#define rep2(x,from,to) for(int x=(from);x<(to);++(x))
#define rep(x,to) rep2(x,0,to)
int main(){
	int m,n,a,b,cost;
	while(cin >> m >> n) {
		if(m==0 && n==0) break;
		int adj[110][110] = {};
		rep(i,m) {
			rep(j,m) {
				if(i==j) continue;
				adj[i][j] = INT_MAX;
			}
		}
		rep(i,n) {
			cin >> a >> b >> cost;
			adj[a][b] = cost;
			adj[b][a] = cost;
		}
		bool used[100] = {};
		int cost[100];
		fill(cost,cost+100,INT_MAX);
		cost[0] = 0;
		int ret = 0;
		while(1) {
			int v = -1;
			rep(i,m) {
				if(!used[i] && (v == -1 || cost[v] > cost[i])) {
					v = i;
				}
			}
			if(v == -1) break;
			used[v] = true;
			ret += cost[v];
			rep(i,m) {
				cost[i] = min(cost[i], adj[v][i]);
			}
		}
		cout <<  ret << endl;
	}
	return 0;
}