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<map>
#include<string>
#include<vector>
#include<algorithm>
#define p pair<int,int>
#define P pair<int,p>
using namespace std;

int Par[100], Rank[100];
int Find(int a) {
	if (Par[a] == a)return a;
	return Par[a]=Find(Par[a]);
}
void unite(int a, int b) {
	a = Find(a);
	b = Find(b);
	if (Rank[a] > Rank[b]) {
		Par[b] = a;
	}
	else if (Rank[a] < Rank[b]) {
		Par[a] = b;
	}
	else {
		Par[b] = a;
		Rank[a]++;
	}
}
int main() {
	int a, b;
	P s[500];
	while (cin >> a >> b, a | b) {
		for (int i = 0; i < a; i++) {
			Par[i] = i; Rank[i] = 0;
		}
		for (int c = 0; c < b; c++) {
			int d, e, f; scanf("%d%d%d", &d, &e, &f);
			s[c] = P(f, p(d, e));
		}
		sort(s, s + b);
		bool k[100]{};
		int sum = 0;
		for (int i = 0; i < b; i++) {
			if (Find(s[i].second.first)!=Find(s[i].second.second)) {
				unite(s[i].second.first, s[i].second.second);
				sum += s[i].first;
			}
		}
		cout << sum << 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 cost[128][128];
int mincost[128];
bool used[128];
int V,E;
void init(){
	rep(i,V)rep(j,V)cost[i][j] = INF;
	fill(mincost,mincost+V,INF);
	fill(used,used+V,false);
}
int prim(){
	mincost[0] = 0;
	int res = 0;
	while(true){
		int v = -1;
		rep(u,V)if(!used[u] && (v == -1 || mincost[u] < mincost[v]))v = u;
		if(v == -1)break;
		used[v] = true;
		res += mincost[v];
		rep(u,V)mincost[u] = min(mincost[u],cost[v][u]);
	}
	return res;
}
int main(){
	int n,m;
	while(scanf("%d%d",&n,&m),n|m){
		V = n;
		init();
		rep(i,m){
			int from,to,pay;
			scanf("%d%d%d",&from,&to,&pay);
			cost[from][to] = pay;
			cost[to][from] = pay;
		}
		printf("%d\n",prim());
	}
	return 0;
}

C++: #include <stdio.h>
#include <stack>
#include <math.h>

using namespace std;



int main(){

	int table[100][100],n,m,sum,fixed[100],count,a,b,cost,minimum,checkTable[100],min_index;

	while(true){
		scanf("%d %d",&n,&m);
		if(n == 0 && m == 0)break;

		for(int i=0; i < n; i++){
			checkTable[i] = 0;
			for(int k=0; k < n; k++)table[i][k] = 0;
		}

		for(int i=0; i < m; i++){
			scanf("%d %d %d",&a,&b,&cost);
			table[a][b] = cost;
			table[b][a] = cost;
		}

		checkTable[0] = 1;
		fixed[0] = 0;
		count = 1;
		sum = 0;

		while(count < n){
			minimum = 1000000000;
			for(int i = 0; i < count; i++){
				for(int k=0; k < n; k++){
					if(table[fixed[i]][k] > 0 && checkTable[k] == 0 && table[fixed[i]][k] < minimum){
						minimum = table[fixed[i]][k];
						min_index = k;
					}
				}
			}

			sum += minimum;
			checkTable[min_index] = 1;
			fixed[count] = min_index;
			count++;
		}

		printf("%d\n",sum);

	}

    return 0;
}

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

#define MAX_N (100)

struct edge { int from, to, cost; };

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

int par[MAX_N];		/// 親
int rank[MAX_N];	/// 木の深さ

/// n要素で初期化
void init ( int n )
{
	for (int i = 0; i < n; ++i) {
		par[i] = i;
		rank[i] = 0;
	}
}

/// 木の根を求める
int find ( int x ) 
{
	if (par[x] == x) {
		return x;
	}
	else {
		return par[x] = find(par[x]);
	}
}

/// xとyの属する集合を合併
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]; }
	}
}

/// xとyが同じ集合に属するか否か
bool same ( int x, int y )
{
	return find(x) == find(y);
}

using namespace std;

int main ( void )
{
	int n, m;

	while (cin >> n >> m, n | m) {
		vector<edge> es;
		for (int i = 0; i < m; ++i) {
			edge e;
			cin >> e.from >> e.to >> e.cost;
			es.push_back(e);
		}

		sort(es.begin(), es.end(), comp);
		init(n);
		int ans = 0;
		for (int i = 0; i < m; ++i) {
			edge e = es[i];
			if (!same(e.from, e.to)) {
				unite(e.from, e.to);
				ans += e.cost;
			}
		}

		cout << ans << endl;
	}
	return 0;
}