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 <functional>
#include <utility>
#include <queue>
#include <list>

using namespace std;

#define N 100

typedef pair<int,int> arw;

int
main (
  int   argc,
  char *argv[ ]
  )
{
  list<arw>::iterator it;
  int i;

  for ( ; ; )
  {
    priority_queue<arw, vector<arw>, greater<arw> > lis;
    list<arw> d[ N ];
    int mk[ N ] = { };
    int res = 0;
    int n, m;

    scanf ( "%d%d", &n, &m );
    if ( n == 0 && m == 0 ) break ;
    for ( i = 0; i < m; ++i )
    {
      int a, b, cost;

      scanf ( "%d%d%d", &a, &b, &cost );
      d[ a ].push_back ( make_pair ( cost, b ) );
      d[ b ].push_back ( make_pair ( cost, a ) );
    }

    /* Prim's Algorithm */
    lis.push ( make_pair ( 0, 0 ) );
    while ( !lis.empty ( ) )
    {
      const arw c = lis.top ( );
      lis.pop ( );

      if ( mk[ c.second ] )
        continue ;

      res += c.first;
      for ( it = d[ c.second ].begin ( ); it != d[ c.second ].end ( ); ++it )
      {
        lis.push ( *it );
      }

      mk[ c.second ] = 1;
    }

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

  return ( EXIT_SUCCESS );
}

C++: #include<cmath>
#include<cctype>
#include<cstdlib>
#include<cstdio>
#include<iostream>
#include<algorithm>
#include<vector>
#include<deque>
#include<string>
#include<queue>
#include<map>
#include<set>
#include<utility>
#include<queue>

const int MAXN = 105;
using namespace std;

struct UnionFind {
  vector<int> data;
  UnionFind(int size) : data(size, -1) { }
  bool unionSet(int x, int y) {
    x = root(x); y = root(y);
    if (x != y) {
      if (data[y] < data[x]) swap(x, y);
      data[x] += data[y]; data[y] = x;
    }
    return x != y;
  }
  bool findSet(int x, int y) {
    return root(x) == root(y);
  }
  int root(int x) {
    return data[x] < 0 ? x : data[x] = root(data[x]);
  }
  int size(int x) {
    return -data[root(x)];
  }
};

struct edge{
  edge(int from,int to):from(from),to(to){}
  int from,to;
};

bool operator<(edge a,edge b){
  if(a.from != b.from)return a.from < b.from;
  else return a.to < b.to;
}

typedef pair<int,pair<int,int> > P;

int main(){
  int n,m;
  while(cin >> n >> m && (n | m) != 0){
    priority_queue<P,vector<P> ,greater<P> > que;
    for (int i = 0; i < m; ++i){
      int a,b,c;
      cin >> a >> b >> c;
      que.push(make_pair(c,make_pair(a, b)));
    }
    UnionFind u(MAXN);
    int ans = 0;
    for (int i = 0; i < m; ++i){
      int from = que.top().second.first;
      int to = que.top().second.second;
      int cost = que.top().first;
      que.pop();
      if(!u.findSet(to, from)){
	//cout << "cost:" << cost << " " << top.to << " " << top.from << endl;
	ans += cost;
	u.unionSet(to,from);
      }
    }
    cout << ans << endl;
  }
  return 0;
}

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

class Node
{
	public:
	vector<int> to,c;
};

class Trl
{
	public:
	int p,c,dc;

	Trl(int p, int c, int dc):p(p),c(c),dc(dc){}
	bool operator<(const Trl& t) const
	{
		return c>t.c;
	}
};


int main()
{
	int n,m;
	int a,b,c;
	while(cin >> n >> m , (n||m))
	{
		Node node[100];
		while(m--)
		{
			cin >> a >> b >> c;
			node[a].to.push_back(b);
			node[b].to.push_back(a);
			node[a].c.push_back(c);
			node[b].c.push_back(c);
		}
		
		int total = 0;
		bool visit[100] = {false};
		priority_queue<Trl> q;
		q.push(Trl(0,0,0));

		while(!q.empty())
		{
			Trl t=q.top(); q.pop();
			if(visit[t.p]) continue;

			visit[t.p] = true;
			total += t.dc;

			for(int i=0; i<node[t.p].to.size(); i++)
			{
				int next = node[t.p].to[i];
				int tc   = node[t.p].c[i];
				if(visit[next]) continue;
				
				q.push(Trl(next,t.c+tc,tc));
			}
		}

		cout << total << endl;


	}
	return 0;
}

C++: #include <bits/stdc++.h>
using namespace std;
using ll = long long;
using P = pair<int, int>;

const int INF = 1001001001;

int cost[111][111];
int minc[111];
bool used[111];
int n, m;

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

int main() {
    while (cin >> n >> m && (n != 0 || m != 0)) {
        for (int i = 0; i < 111; i++) {
            for (int j = 0; j < 111; j++) {
                cost[i][j] = INF;
            }
        }
        for (int i = 0, a, b, c; i < m; i++) {
            cin >> a >> b >> c;
            cost[a][b] = cost[b][a] = c;
        }
        int ans = prim();
        cout << ans << endl;
    }
}