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 <queue>
#include <vector>

using namespace std;

class Bridge
{
public:
	int from;
	int to;
	int cost;

	Bridge() : from(0), to(0), cost(0) {}
	Bridge(const Bridge& b) : from(b.from), to(b.to), cost(b.cost) {}

	bool operator > (const Bridge& b) const
	{
		return cost > b.cost;
	}

	bool operator < (const Bridge& b) const
	{
		return cost < b.cost;
	}
};



int nCity, nBridge;

Bridge bridge[100];
bool city[100];

int main()
{
	while( 1 )
	{
		//load data
		cin >> nCity >> nBridge;
		if(nCity == 0 && nBridge == 0)
		{
			break;
		}

		for(int i=0; i<nBridge; i++)
		{
			cin >> bridge[i].from >> bridge[i].to >> bridge[i].cost;
		}

		for(int i=0; i<nCity; i++)
		{
			city[i] = false;
		}

		//set initial node to queue
		priority_queue<Bridge, vector<Bridge>, greater<Bridge> > que;
		for(int i=0; i<nBridge; i++)
		{
			if(bridge[i].from == 0 || bridge[i].to == 0)
			{
				que.push(bridge[i]);
			}
		}

		city[0] = true;

		//iteration
		int totalCost = 0;
		while(!que.empty())
		{
			//end check
			bool isEnd = true;
			for(int i=0; i<nCity; i++)
			{
				if(!city[i])
				{
					isEnd = false;
					break;
				}
			}

			if(isEnd)
			{
				break;
			}

			//check highest priority node
			Bridge current = que.top();
			que.pop();

			totalCost += current.cost;

			int next = 0;
			if(!city[current.to])
			{
				city[current.to] = true;
				next = current.to;
			}
		
			if(!city[current.from])
			{
				city[current.from] = true;
				next = current.from;
			}

			for(int i=0; i<nBridge; i++)
			{
				if(bridge[i].to == next || bridge[i].from == next)
				{
					if(!city[bridge[i].to] || !city[bridge[i].from])
					{
						que.push(bridge[i]);
					}
				}
			}
		}

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

C++: #include <iostream>
#include <cstdio>
#include <cmath>
#include <algorithm>
#include <string>
#include <map>
#include <bitset>
#include <vector>
#include <queue>

using namespace std;

typedef long long ll;
#define FOR(i,a,b)   for(ll i = (a); i < (b); i++ )
#define REP(i, n)    FOR(i,0,n)
typedef pair< int, int >   cp2;
typedef pair< int, cp2 >   cp3;
#define fi first
#define se second
#define sec  se.fi
#define thr  se.se
const ll mod = 1000000007;
//              123456789


 

///////////////////////////////////////////////
//
//
///////////////////////////////////////////////

////////////////////////////////////////////////
////////////////////////////////////////////////



priority_queue< cp3, vector<cp3>, greater<cp3> >p;
cp3 now;

int g[112];

int find( int key ){
	//cout<<key<<" "<<g[key]<<endl;
	if( g[key] < 0 ) return key;
	return g[key] = find( g[key] );
}

void unite( int x, int y ){
	x = find( x );
	y = find( y );
	if( x == y ) return;
	
	if( g[x] < g[y] ) swap( x, y );
	if( g[x] == g[y] ) g[y]--;//??±??????x???????????????
	//g[y] += g[x];		 //????????°???x??????????°???????
	g[x] = y;
}

int a, b;
int c;
int N;
int M;
int ans;

int main(){
	
	while( cin>>N>>M, N && M){
		
		ans = 0;
		fill( g, g+112, -1 );
	
		REP( i, M ){
			scanf("%d %d %d",&a, &b, &c);
			p.push( cp3( c, cp2(a, b) ) );	
		}
	
		while( !p.empty() ){
			now = p.top();
			p.pop();
			
			if( find(now.sec) != find(now.thr) ){
				unite( now.sec, now.thr );
				ans += now.fi;
			}
		}
		
		cout<<ans<<endl;
	}


	return 0;

}

C++: #include <bits/stdc++.h>
using namespace std;
#define MAX_INT 10000
#define PII pair<int, int>
#define VPII vector<PII >

int solve(int n, const vector<VPII >& adjacent) {
  vector<bool> used(n, false);
  int result = 0;
  priority_queue<PII, VPII, greater<PII > > q;
  for (auto v : adjacent[0]) q.push(v);
  used[0] = true;
  while(q.size() > 0) {
    PII current = q.top(); q.pop();
    if (!used[current.second]) {
      used[current.second] = true;
      result += current.first;
      for (auto v : adjacent[current.second]) q.push(v);
    }
  }

  return result;
}

int main() {
  int n, m;
  while (cin >> n >> m, n != 0) {
    vector<VPII > adjacent(n);
    for (int i = 0; i < m; i++) {
      int a, b, c;
      cin >> a >> b >> c;
      adjacent[a].push_back(make_pair(c, b));
      adjacent[b].push_back(make_pair(c, a));
    }
    cout << solve(n, adjacent) << endl;
  }
}

C++: #include <bits/stdc++.h>
#include <algorithm>
using namespace std;
using namespace std;
#define INF 1000000000
typedef long long int lli;
typedef pair<int,int> P;

const int MAX_V=100;
int cost[MAX_V][MAX_V];
int mincost[MAX_V];
bool used[MAX_V];

int prim(int V){
    for(int i=0; i<V; ++i){
        mincost[i]=INF;
        used[i]=false;
    }
    mincost[0]=0;
    int res=0;

    while(true){
        int v=-1;
        for(int u=0; u<V; ++u){
            if(!used[u]&&(v==-1||mincost[u]<mincost[v])) v=u;
        }
        if(v==-1) break;
        used[v]=true;
        res+=mincost[v];
        for(int u=0; u<V; ++u){
            mincost[u]=min(mincost[u],cost[v][u]);
        }
    }
    return res;
}

int main(){
    int n,m;
    while(cin>>n>>m){
        if(n==0&&m==0) break;
        for(int i=0;i<n;++i)for(int j=0;j<n;++j) cost[i][j]=INF;
        for(int i=0; i<m; ++i){
            int a,b,c;
            cin >> a >> b >> c;
            cost[a][b]=cost[b][a]=c;
        }
        cout << prim(n) << "\n";
    }
    return 0;
}