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<cstdio>
#include<algorithm>
#include<vector>
#define rep(i,a) for( int i = 0; i != (a); ++i )

struct edge
{
	int from, to, cost;

	edge( int from, int to, int cost )
	:	from( from ), to( to ), cost( cost )
	{}
};

int n, m;
std::vector<edge> es;

int par[100], rank[100];

void init()
{
	rep( i, n )
		par[i] = i, rank[i] = 0;

	return;
}

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

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

	if( rank[x] > rank[y] )
		par[y] = x;
	else
	{
		par[x] = y;
		if( rank[x] == rank[y] )
			++rank[y];
	}

	return;
}

bool same( int x, int y )
{
	return find( x ) == find( y );
}

int main()
{
	while( scanf( "%d%d", &n, &m ), n|m )
	{
		es.clear();
		init();
		rep( i, m )
		{
			int a, b, c;
			scanf( "%d%d%d", &a, &b, &c );
			es.push_back( edge( a, b, c ) );
		}

		std::sort( es.begin(), es.end(), []( const edge& e1, const edge& e2 ){ return e1.cost < e2.cost; } );

		int ans = 0;
		rep( i, es.size() )
		{
			edge& e = es[i];
			if( !same( e.from, e.to ) )
			{
				ans += e.cost;
				unite( e.from, e.to );
			}
		}

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

	return 0;
}

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

const int INF = 1000000;
int main(){
	int n,m;
	while(cin >> n >> m){
		if(!n && !m)
			break;
		int bridge[100][100];
		int a,b,cost;
		for(int i=0;i<100;i++){
			for(int j=0;j<100;j++){
				if(i==j)
					bridge[i][j] = 0;
				else
					bridge[i][j] = INF;
			}
		}
		for(int i=0;i<m;i++){
			cin >> a >> b >> cost;
			bridge[a][b] = cost;
			bridge[b][a] = cost;
		}
		
		//ツフツδ債イツド
		for(int k=0;k<n;k++){
			for(int i=0;i<n;i++){
				for(int j=0;j<n;j++){
					int dis = bridge[i][k]+bridge[k][j];
					if(dis < bridge[i][j]){
						bridge[i][j] = dis;
					}	
				}
			}
		}

		
		int min[10000];
		int pos = 0;
		for(int i=0;i<n;i++){
			for(int j=0;j<n;j++){
				if(i<j){
					min[pos++] = bridge[i][j];
				}
			}
		}
		sort(min,min+pos-1);
		int sum = 0;
		for(int i=0;i<n-1;i++){
			sum+=min[i];
		}
		cout << sum << endl;
	}
	return 0;
}

C++: #include <cstdio>
#include <algorithm>
using namespace std;
struct unionfind {
    int par[100], rank[100];
    unionfind(int n) {
        for (int i=0; i<n; i++) {
            par[i]=i;
            rank[i]=0;
        }
    }
    int find(int x) {
        if (par[x]==x) {
            return x;
        } else {
            return par[x]=find(par[x]);
        }
    }
    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]++;
        }
    }
    bool same(int x, int y) {
        return find(x)==find(y);
    }
};
struct edge {
    int u, v, cost;
    edge(){}
    edge(int u, int v, int cost) : u(u), v(v), cost(cost) {}
};
bool comp(const edge& e1, const edge& e2) {
    return e1.cost<e2.cost;
}
int main() {
    int n, m;
    while (scanf("%d%d",&n,&m)) {
        if (!n&&!m) break;
        unionfind uf(n);
        edge bridge[m];
        for (int i=0; i<m; i++) {
            int a, b, cost; scanf("%d%d%d",&a,&b,&cost);
            bridge[i]=edge(a,b,cost);
        }
        sort(bridge,bridge+m,comp);
        int res=0;
        for (int i=0; i<m; i++) {
            edge e=bridge[i];
            if (!uf.same(e.u,e.v)) {
                uf.unite(e.u,e.v);
                res+=e.cost;
            }
        }
        printf("%d\n",res);
    }
}

C++: #include <bits/stdc++.h>
using namespace std;

typedef pair<int,int> P;

int main() {
  int n,m;
  while(cin >> n >> m && n) {
    bool u[n];
    memset(u,0,sizeof(u));
    vector<P> v[n];
    for(int i=0; i<m; i++) {
      int x,y,z;
      cin >> x >> y >> z;
      v[x].push_back(P(y,z));
      v[y].push_back(P(x,z));
    }
    int ans=0;
    priority_queue<P,vector<P>,greater<P> > que;
    que.push(P(0,0));
    while(!que.empty()) {
      P p=que.top();que.pop();
      int x=p.second,c=p.first;
      if(u[x]) continue;
      u[x]=1;
      ans+=c;
      for(int i=0; i<v[x].size(); i++) {
        int y=v[x][i].first;
        if(!u[y]) que.push(P(v[x][i].second,y));
      }
    }
    cout << ans << endl;
  }
  return 0;
}