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<cstdio>
#include<algorithm>
#include<queue>
#include<cstring>
#include<cstdlib>
#include<vector>
#define MAX_V 1000
#define INF 1<<29
#define cl(a,b) for(int i=0;i<a;i++)for(int j=0;j<b;j++)cost[i][j] = INF;
#define de(a)  for(int i=0;i<a;i++){cout << mincost[i] << " "; if(i == a-1){cout << endl;}}
#define de2(a,b) for(int I=0;I<a;I++){for(int j=0;j<b;j++){cout << cost[I][j] << " ";}cout << endl;}cout << endl;
using namespace std;

int cost[MAX_V][MAX_V];
int mincost[MAX_V];
bool used[MAX_V];
int V;
bool connect[10000];

int prime()
{
  for(int i=0;i<V;++i)
    {
      mincost[i]=INF;
      used[i]=false;
    }
  mincost[0] = 0;
  int res = 0;
  while(true)
    {
      int v = -1; 
      for(int u = 0; u<V ; u++ )
	{
	  if(connect[u] && !used[u] && (v == -1 || mincost[u] < mincost[v]))
	    {
	      v = u;
	    }
	}
      if(v == -1)break;
      used[v] = true;
      res += mincost[v];
      for(int u = 0; u < V; u++)
	{
	  mincost[u] = min(mincost[u],cost[v][u]);	  
	}
    }
  return res;
}

int main()
{
  int n,m,a,b;
  while(true)
    {
      cin >> n >> m;
      if(n == 0 && m == 0)break;
      cl(n,n);
      memset(connect,false,sizeof(connect));
      V = n; // VÍ¸_
      for(int i=0;i<m;i++)
	{
	  cin >> a >> b;
	  cin >> cost[a][b];
	  cost[b][a] = cost[a][b];
	  connect[a] = true;
	  connect[b] = true;
	}
      cout << prime() << endl;
    }
}

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 ;
	par[x] = y;
}
bool same(int x,int y){
	return find(x) == find(y);
}
int main(){
	int n,m;
	while(scanf("%d%d",&n,&m),n|m){
		edge Data[128];
		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<stdio.h>
#include<string.h>
#include<math.h>
int main(void)
{
	int a,s,d[101],f[101],g[101],h,i,j,size[101],ban[101];
	int z,x,q;
	scanf("%d %d",&a,&s);
	for(i=0;i<a;i++){
		ban[i]=i;
		size[i]=1;
	}
	for(i=0;i<s;i++) scanf("%d %d %d",&d[i],&f[i],&g[i]);
	for(i=0;i<s;i++){
		if(d[i]>f[i]) h=d[i]; d[i]=f[i]; f[i]=h;
		for(j=i+1;j<s;j++){
			if(g[i]>g[j]){
				h=g[i]; g[i]=g[j]; g[j]=h;
				h=d[i]; d[i]=d[j]; d[j]=h;
				h=f[i]; f[i]=f[j]; f[j]=h;
			}
		}
	}
	/*for(i=0;i<s;i++)
		printf("%d %d %d\n",d[i],f[i],g[i]);*/
	for(i=0;i<s;i++){
	//	printf("%d %d %d\n\n",d[i],f[i],g[i]);
		z=d[i]; x=f[i];
		while(ban[z]!=z) z=ban[z];
		while(ban[x]!=x) x=ban[x];
		if(z!=x){
			q+=g[i];
			if(size[z]>size[x]) ban[x]=z;
			else if(size[z]<=size[x]) ban[z]=x;
		}
	}
	printf("%d\n",q);
	return 0;
}

C++: #include<stdio.h>
#include<string.h>
#include<math.h>
int main(void)
{
	int a,s,d[101],f[101],g[101],h,i,j,size[101],ban[101];
	int z,x,q;
	scanf("%d %d",&a,&s);
	for(i=0;i<a;i++){
		ban[i]=i;
		size[i]=1;
	}
	for(i=0;i<s;i++) scanf("%d %d %d",&d[i],&f[i],&g[i]);
	for(i=0;i<s;i++){
		if(d[i]>f[i]) h=d[i]; d[i]=f[i]; f[i]=h;
		for(j=i+1;j<s;j++){
			if(g[i]>g[j]){
				h=g[i]; g[i]=g[j]; g[j]=h;
				h=d[i]; d[i]=d[j]; d[j]=h;
				h=f[i]; f[i]=f[j]; f[j]=h;
			}
		}
	}
	for(i=0;i<s;i++){
		z=d[i]; x=f[i];
		while(ban[z]!=z) z=ban[z];
		while(ban[x]!=x) x=ban[x];
		if(z!=x){
			q+=g[i];
			if(size[z]>size[x]) ban[z]=x;
			else if(size[z]<size[x]) ban[x]=z;
			else{
				ban[x]=z;
				size[x]++;
			}
		}
	}
	printf("%d\n",q);
	return 0;
}

C++: #include<bits/stdc++.h>
#define rep(i,n)for(int i=0;i<n;i++)
using namespace std;

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

int main() {
	int n, m;
	while (scanf("%d%d", &n, &m), n) {
		memset(cost, 0x3f, sizeof(cost));
		rep(i, m) {
			int a, b, c; scanf("%d%d%d", &a, &b, &c);
			cost[a][b] = c; cost[b][a] = c;
		}
		memset(mincost, 0x3f, sizeof(mincost));
		memset(used, 0, sizeof(used));
		mincost[0] = 0;
		int ans = 0;
		while (true) {
			int v = -1;
			rep(i, n) {
				if (!used[i] && (v == -1 || mincost[i] < mincost[v]))
					v = i;
			}
			if (v == -1)break;
			used[v] = true;
			ans += mincost[v];
			rep(i, n)mincost[i] = min(mincost[i], cost[v][i]);
		}
		printf("%d\n", ans);
	}
}