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 <vector>
#include <cstring>
#include <queue>

#define FOR(i,a,b) for(int i=(a);i<(b);i++)
using namespace std;

const int INF = 100000000;

struct edge {
    int to, cost;
    bool operator<(const edge& r)const{
        return cost>r.cost;
    }
};

// state = edge
// struct state {
//     int from, d;
// };
vector<vector<edge> > G;
int V;

bool used[111];
int prim(){
    int sum=0;
    int es=0;
    memset(used,0,sizeof(used));
    priority_queue<edge> q;
    q.push({0,0});
    while(es!=G.size()){
        edge e=q.top(); q.pop();
        es++;
        used[e.to]=1;
        int from=e.to;
        //cout<<" "<<from<<endl;
        sum+=e.cost;
        FOR(i,0,G[from].size()){
            if(!used[G[from][i].to])
                q.push(G[from][i]);
        }
    }
    return sum;
}

int main(){
    int m;
    while(1){
        cin>>V>>m;
        if(!(m||V))break;
        G=vector<vector<edge> >(V);
        FOR(i,0,m){
            int a,b,cost;cin>>a>>b>>cost;
            G[a].push_back({b,cost});
            G[b].push_back({a,cost});
        }
        cout<<prim()<<endl;
    }
}

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

struct Edge {
	int s;
	int t;
	int cost;
	Edge() {}
	Edge(int s, int t, int cost) : s(s), t(t), cost(cost) {}
};
bool operator < (const Edge& e, const Edge& f) { return e.cost < f.cost; }

int root(int* par, int x)
{
	if (x==par[x]) return x;
	else return par[x] = root(par, par[x]);
}

void unite(int* par, int x, int y)
{
	par[root(par, x)] = root(par, y);
}

bool isSame(int* par, int x, int y)
{
	return root(par, x) == root(par, y);
}

int main()
{
	int n, m;
	while (true) {
		std::cin >> n >> m;
		if (n == 0) break;
		std::vector<Edge> edge_list;
		for (int i=0; i<m; i++) {
			int s, t, cost;
			std::cin >> s >> t >> cost;
			edge_list.push_back( Edge(s, t, cost) );
		}
		std::sort(edge_list.begin(), edge_list.end());
		int* par = new int[n];
		for (int i=0; i<n; i++) par[i] = i;
		int res = 0;
		int count = 0;
		for (int i=0; i<edge_list.size(); i++) {
			if (isSame(par, edge_list[i].s, edge_list[i].t)) continue;
			unite(par, edge_list[i].s, edge_list[i].t);
			res += edge_list[i].cost;
			count++;
			if (count == n-1) break;
		}
		std::cout << res << std::endl;
		delete[] par;
	}
	return 0;
}

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 <iostream>
#include <vector>
#include <algorithm>
using namespace std;

const int UF_SIZE = 128;
int UF[UF_SIZE];

void UF_init() {
	for(int i = 0; i < UF_SIZE; i++) {
		UF[i] = i;
	}
}

int UF_indx(int a) {
	if(a == UF[a])
		return a;
	else
		return UF_indx(UF[a]);
}

int UF_merge(int a, int b) {
	UF[UF_indx(a)] = UF_indx(b);
}

struct bridge {
	int a, b;
	int cost;
	bridge(int a_, int b_, int cost_) {
		a = a_; b = b_;
		cost = cost_;
	}

	bool operator<(const bridge obj) const {
		return cost < obj.cost;
	}
};

int main() {
	int n, m;
	while(1) {
		cin >> n >> m;
		if(n == 0 && m == 0)
			break;
		vector<bridge> v;
		UF_init();
		for(int i = 0; i < m; i++) {
			int a, b;
			int cost;
			cin >> a >> b >> cost;
			v.push_back(bridge(a, b, cost));
		}

		sort(v.begin(), v.end());
		int ans = 0;
		for(int i = 0; i < v.size(); i++) {
			if(UF_indx(v[i].a) != UF_indx(v[i].b)) {
				UF_merge(v[i].a, v[i].b);
				ans += v[i].cost;
			}
		}
		cout << ans << endl;
	}
}