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

int par[120];
int rnk[120];
struct edge { int u, v, cost; };
bool comp(const edge&e1, const edge& e2) {
	return e1.cost < e2.cost;
}

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

int find(int a) {
	if (par[a] == a)return a;
	else return par[a] = find(par[a]);
}

void unite(int x, int y) {
	x = find(x);
	y = find(y);
	if (x == y)return;

	if (rnk[x] < rnk[y])par[x] = y;
	else {
		par[y] = x;
		if (rnk[x] == rnk[y])rnk[x]++;
	}
}

bool same(int x, int y) {
	return find(x) == find(y);
}
int main() {
	int n, m;
	while (cin >> n >> m, n, m) {
		edge es[1000];
		for (int i = 0;i < m;i++) {
			int a, b, c;
			cin >> a >> b >> c;
			es[i].u = a;
			es[i].v = b;
			es[i].cost = c;
		}
		sort(es, es + m, comp);
		init(n);
		int ans = 0;
		for (int i = 0;i < m;i++) {
			edge e = es[i];
			if (!same(e.u, e.v)) {
				unite(e.u, e.v);
				ans += e.cost;
			}
		}
		cout << ans << endl;
	}
	return 0;
}

C++: #include<iostream>
#include<vector>
#include<algorithm>
#define N 20000

using namespace std;

int Prim(const vector< vector<int> >& data){
  vector<bool> is_reached(data.size(), false);
  vector<int> cost(data.size(), N);
  int i, j, ans;
  i = 0;
  ans = 0;
  cost[i] = 0;
  while(i != -1){
    ans += cost[i];
    is_reached[i] = true;
    for(j=0; j<data[i].size(); ++j){
      cost[j] = min(cost[j], data[i][j]);
    }
    for(i=-1, j=0; j<is_reached.size(); ++j){
      if(!is_reached[j] && (i < 0 || cost[i] > cost[j])) i = j;
    }
  }
  return ans;
}

int main(){
  int n, m;
  int a, b, c;

  while(1){
    cin >> n >> m;
    if(n == 0 && m == 0) break;

    vector< vector<int> > data(n, vector<int>(n, N));
    for(int i=0; i<m; ++i){
      cin >> a >> b >> c;
      data[a][b] = c;
      data[b][a] = c;
    }
    cout << Prim(data) << endl;
  }
  return 0;
}

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<stack>
#include<queue>
#include<map>
#include<string>
#include<algorithm>
#include<cstring>
#include<cmath>
#include<cstdio>
using namespace std;

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

const int maxn = 101, maxm = 5500,INF = 11100;

int cost[maxn][maxn];
int mincost[maxn];
bool used[maxn];
int n,m,a,b;

int main()
{
    while(cin>> n >> m &&(n&&m))
    {
        memset(cost,INF,sizeof(cost));
        memset(used,false,sizeof(used));
        memset(mincost,INF,sizeof(mincost));

        REP(m)
        {
            cin >> a >> b ;
            cin >>cost[a][b];
            cost[b][a] = cost[a][b];

        }
        mincost[0] = 0;
        int ans = 0;

        while(true)
        {
            int minv = -1;
            REP(n)if(!used[i] &&(minv == -1 ||mincost[i] < mincost[minv] )) minv = i;
            //cout << "v" << minv << endl;
            if(minv == -1) break;
            used[minv] = true;
            ans += mincost[minv];
            //cout<<minv<<":" << mincost[minv] << endl;
            
            REP(n) mincost[i] = min(mincost[i], cost[minv][i]);
        }
        
        cout << ans << endl;

    }

    return 0;
}