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 <string>
#include <vector>
using namespace std;

const int INF = 100000;
struct Edge { int from, to, cost; };

int main() {
    int n, m;
    while (cin >> n >> m, n) {
        vector<Edge> G;
        int a, b, cost;
        for (int i=0; i<m; ++i) {
            cin >> a >> b >> cost;
            G.push_back((Edge){ a, b, cost });
            G.push_back((Edge){ b, a, cost });
        }
        int ret = 0;
        bool used[100] = {};
        used[0] = true;
        while (1) {
            int k, mn = INF;
            for (int i=0; i<(int)G.size(); ++i) {
                if (used[G[i].from] && ! used[G[i].to] && G[i].cost < mn) {
                    mn = G[i].cost;
                    k = i;
                }
            }
            if (mn == INF) break;
            used[G[k].to] = true;
            ret += G[k].cost;
        }
        cout << ret << endl;
    }
    return 0;
}

C++: #include <algorithm>
#include <climits>
#include <cmath>
#include <cstdio>
#include <cstdlib>
#include <iostream>
#include <limits>
#include <stack>
#include <string>
#include <vector>

#define FOR(i,k,n) for (int (i)=(k); (i)<(n); ++(i))
#define rep(i,n) FOR(i,0,n)
#define pb push_back
#define eb emplace_back
#define all(v) begin(v), end(v)

using namespace std;
typedef long long ll;
typedef unsigned long long ull;
typedef vector<int> vi;
typedef vector<vector<int> > vvi;
template<class T> using vv=vector<vector< T > >;

struct union_find {
    int n;
    vi d;
    union_find() {}
    union_find(int n_): n(n_), d(n, -1) {}
    int root(int v) {
        if (d[v] < 0) {
            return v;
        }
        return d[v] = root(d[v]);
    }
    int size(int v) {
        return -d[root(v)];
    }
    bool unite(int x, int y) {
        x = root(x);
        y = root(y);
        if (x == y) {
            return false;
        }
        if (size(x) < size(y)) {
            swap(x, y);
        }
        d[x] += d[y];
        d[y] = x;
        return true;
    }
};

int main() {
    while (true) {
        int n, m;
        cin >> n >> m;
        if ( n == 0 ) { break; }
        vvi edges(m);
        rep (i, m) {
            int a, b, cost;
            cin >> a >> b >> cost;
            edges[i] = {cost, a, b};
        }
        sort(all(edges));

        int ans = 0;
        union_find uf(n);
        rep (i, m) {
            if ( uf.unite(edges[i][1], edges[i][2]) ) {
                ans += edges[i][0];
            }
        }
        printf("%d\n", ans);
    }
    return 0;
}

C++: #include<iostream>
#include<utility>
#include<queue>
#include<functional>
#include<algorithm>
#include<cstring>
#include<vector>
#include<climits>
#include<map>
using namespace std;
#define FOR(i,n) for(int i=0;i<(int)n;i++)
#define FORI(i,k,n) for(int i=k;i<(int)n;i++)
#define ALL(x) (x).begin(),(x).end()
#define INF (2<<25)
typedef pair<int,int> pii;
typedef vector<int> vi;

int main()
{
	while(true)
	{
		int n,m;
		int cost[200][200];
		bool used[200]={};
		
		cin>>n>>m;
		if(n==0&&m==0)break;
		FOR(i,200)FOR(j,200)cost[i][j]=INF;
		
		FOR(i,m)
		{
			int a,b,c;
			cin>>a>>b>>c;
			cost[a][b]=cost[b][a]=c;
		}
		
		priority_queue< pii,vector<pii>,greater<pii> > que;
		que.push(pii(0,0));
		int ans=0;
		while(!que.empty())
		{
			pii now=que.top();que.pop();
			if(used[now.second])continue;
			used[now.second]=true;
			ans+=now.first;
			FOR(i,200)
			{
				if(cost[now.second][i]==INF)continue;
				que.push(pii(cost[now.second][i],i));
			}
		}
		cout<<ans<<endl;
		
		
	}
}

C++: #include <iostream>
#include <algorithm>
#include <cmath>
using namespace std;

int N, M , A[10010], B[10010], COST[10010];
int P[10010];
int Rank[10010];
pair<int, int> bridge[10010];

void init(int N){
	for(int i = 0; i < N; ++i){
		P[i] = i;
		Rank[i] = 0;
	}
}

int root(int a){
	if(P[a] == a) return a;
	return (P[a] = root(P[a]));
}

bool IsSameSet(int a, int b){
	return root(a) == root(b);
}

void unite(int a, int b){
	P[root(a)] = root(b);
}

void link(int a, int b){
	if(Rank[a] > Rank[b]){
		P[b] = a;
	} else {
		P[a] = b;
		if(Rank[a] == Rank[b]) Rank[a]++;
	}
}

int main(){
	int a,b;
	while(cin >> N >> M, N > 0 && M > 0){
		init(N);
		for(int i=0; i<M; i++){
			cin >> A[i] >> B[i] >> COST[i];
			bridge[i].first = COST[i];
			bridge[i].second = i;
		}		
		sort(bridge, bridge + M);
		int sum = 0;
		for (int i = 0; i < M; ++i){
			int a = A[bridge[i].second];
			int b = B[bridge[i].second];
			if(IsSameSet(a,b)) continue;
			unite(a,b);
			sum += bridge[i].first;
		}
		cout << sum << endl;

	}

}