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<iostream>
#include<string>
#include<map>
#include<queue>
#include<set>

using namespace std;

#define rep(i,n) for(int i=0;i<n;i++)
#define reps(i,n) for(int i=1;i<=n;i++)

class S{
	public:
	int x,now,bef;
	S(int x,int now,int bef):x(x),now(now),bef(bef){}
	bool operator<(const S&a)const{
		return now>a.now;
	}
};

int main(){
	while(1){
		int n,m;
		cin>>n>>m;
		if(n==0)break;
		
		int to[111][111]={0};
		rep(i,m){
			int a,b,c;
			cin>>a>>b>>c;
			
			to[a][b]=c;
			to[b][a]=c;
		}
		
		priority_queue<S> que;
		que.push(S(0,0,-1));
		
		int ans=0;
		
		int visit[111]={0};
		while(1){
			if(que.empty())break;
			
			S u = que.top();
			que.pop();
			
			if(visit[u.x]==1)continue;
			visit[u.x]=1;
			
			if(u.bef!=-1){
				ans += to[u.x][u.bef];
			}
			
			rep(i,n){
				if(to[u.x][i]==0)continue;
				if(visit[i]==1)continue;
				que.push( S(i ,to[u.x][i]+u.now ,u.x) );
			}
		}
		printf("%d\n",ans);
	}
}

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

const int MAX_N = 100;
const int INF = 100000;

int n, m;
int cost[MAX_N][MAX_N], mincost[MAX_N];
bool used[MAX_N];

int prim(){
	for (int i = 0; i < n; ++i)
		mincost[i] = INF;
	mincost[0] = 0;
	int res = 0;
	while (1){
		int v = -1;
		for (int i = 0; i < n; ++i){
			if (!used[i] && (v == -1 || mincost[i] < mincost[v]))
				v = i;
		}
		if (v == -1)
			break;
		used[v] = true;
		res += mincost[v];

		for (int i = 0;  i < n; ++i)
			mincost[i] = std::min(mincost[i], cost[v][i]);
	
	}
	return res;
}

int main(){
	while (1){
		std::cin >> n >> m;
		if (n == 0 && m == 0)
			break;
		std::memset(used, 0, n);
		for (int i = 0; i < n; ++i){
			for (int j = 0; j < n; ++j)
				cost[i][j] = INF;
		}
		int a, b, c;

		for (int i = 0; i < m; ++i){
			std::cin >> a >> b >> c;
			cost[a][b] = c;
			cost[b][a] = c;
		}
		std::cout << prim() << std::endl;
	}
	return 0;
}

C++: #include "Graph.hpp"
#include<iostream>
#include<vector>
#include<queue>
using namespace std;

Graph creat_graph(int n, int m);
int search_prim(Graph prim, int n);

vector<int> ans;
vector<vector<int>> cost(100,vector<int>(100,0));

int main(){
  int n,m;
 
  
  while(cin >> n >> m, n){     
    Graph prim = creat_graph(n,m);   /*creat graph*/
    ans.push_back(search_prim(prim,n));   /*make answer*/
  }
  
  for(int i: ans){
    cout << i << endl;
  }
  return 0;
}


 Graph creat_graph(int n,int m){
    Graph prim(n);
    int a,b,cost_t;

    for(int i=0; i<m; i++){
      cin >> a >> b >> cost_t;
      prim.connect(a,b);
      cost[a][b] = cost_t;
      cost[a][b] = cost_t;
    }
    return prim;
  }
    
int search_prim(Graph prim, int n){
  int current,cost_sum;
  typedef pair<int, int> PII;
  vector<bool> frag(n,false);
  priority_queue < PII, vector < pair <int, int> >, greater < pair <int, int> > > que;
  /*cost,next_node*/
  
  cost_sum = 0;
  current = 0;
  frag[0] = true;
  for(int k=0; k<n-1; ++k){
     vector<int> near = prim.neighbours(current);

     for(int j:near){
       que.push(PII(cost[current][j],j));
     }

     while(1){
       if(frag[que.top().second] == false){
	 cost_sum += que.top().first;
	 frag[que.top().second] = true;
	 current = que.top().second;
	 break;
	 }
     }
     que.pop();
  }
  return cost_sum;
}