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 <utility>
#define INF 1000000
#define MAX_N 100
using namespace std;
int n,m;
int cost[MAX_N][MAX_N];
int mincost[MAX_N];
bool used[MAX_N];

void solve() {
  for(int i=0;i<n;i++) {
    mincost[i] = INF;
    used[i] = false;
  }
  mincost[0] = 0;
  int res = 0;
  while(true) {
    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;
    res += mincost[v];
    used[v] = true;

    for(int i=0;i<n;i++) {
      mincost[i] = min(mincost[i],cost[v][i]);
    }
  }
  cout << res << endl;
}

int main() {
  while(cin >> n >> m) {
    if(n==0&&m==0) break;
    for(int i=0;i<100;i++) {
      for(int j=0;j<100;j++) {
        cost[i][j] = INF;
      }
    }
    for(int i=0;i<m;i++) {
      int f,t,c;
      cin >> f >> t >> c;
      cost[f][t] = c;
      cost[t][f] = c;
    }
    solve();
  }
}

C++: #include<stdio.h>
#include<string.h>
#include<math.h>
int a,s,d[501],f[501],g[501],h,size[101],ban[101];
int z,x,q;
int main(void)
{
	int i,j;
	while(1){
		scanf("%d %d",&a,&s);
		if(a==0&&s==0) break;
		for(i=0;i<a;i++){
			ban[i]=i;
			size[i]=1;
		}
		for(i=0;i<s;i++) scanf("%d %d %d",&d[i],&f[i],&g[i]);
		for(i=0;i<s-1;i++){
			for(j=i+1;j<s;j++){
				if(g[i]>g[j]){
					h=g[i]; g[i]=g[j]; g[j]=h;
					h=d[i]; d[i]=d[j]; d[j]=h;
					h=f[i]; f[i]=f[j]; f[j]=h;
				}
			}
		}
		q=0;
		for(i=0;i<s;i++){
			//if(d[i]>f[i]) h=d[i]; d[i]=f[i]; f[i]=h;
			z=d[i]; x=f[i];
			while(ban[z]!=z) z=ban[z];
			while(ban[x]!=x) x=ban[x];
			if(z!=x){
				q+=g[i];
				if(size[z]>size[x]) ban[x]=z;
				else ban[z]=x;
			}
		}
		printf("%d\n",q);
	}
	return 0;
}

C++: #include <bits/stdc++.h>

using namespace std;

typedef long long ll;
typedef vector<int> vi;
typedef vector<ll> vl;
typedef complex<double> P;
typedef pair<int,int> pii;
#define REP(i,n) for(ll i=0;i<n;++i)
#define REPR(i,n) for(ll i=1;i<n;++i)
#define FOR(i,a,b) for(ll i=a;i<b;++i)

#define DEBUG(x) cout<<#x<<": "<<x<<endl
#define DEBUG_VEC(v) cout<<#v<<":";REP(i,v.size())cout<<" "<<v[i];cout<<endl
#define ALL(a) (a).begin(),(a).end()

#define MOD (ll)(1e9+7)
#define ADD(a,b) a=((a)+(b))%MOD
#define FIX(a) ((a)%MOD+MOD)%MOD

// http://www.prefield.com/algorithm/container/union_find.html
struct UnionFind {
  vector<int> data;
  UnionFind(int size) : data(size, -1) { }
  bool unionSet(int x, int y) {
    x = root(x); y = root(y);
    if (x != y) {
      if (data[y] < data[x]) swap(x, y);
      data[x] += data[y]; data[y] = x;
    }
    return x != y;
  }
  bool findSet(int x, int y) {
    return root(x) == root(y);
  }
  int root(int x) {
    return data[x] < 0 ? x : data[x] = root(data[x]);
  }
  int size(int x) {
    return -data[root(x)];
  }
};

int main(){
  while(true){
    int n,m;
    cin>>n>>m;
    if(n==0 && m==0)break;
    int res = 0;
    vector< pair<int,pii> > edges(m);
    REP(i,m){
      int a,b,c;
      cin>>a>>b>>c;
      edges[i] = make_pair(c,make_pair(a,b));
    }
    sort(ALL(edges));
    UnionFind uf(n);
    REP(i,m){
      int a,b,c;
      c = edges[i].first;
      a = edges[i].second.first;
      b = edges[i].second.second;
      if(!uf.findSet(a,b)){
        uf.unionSet(a,b);
        res += c;
      }
    }
    cout << res << endl;
  }
  return 0;
}

C++: #include<cmath>
#include<cctype>
#include<cstdlib>
#include<cstdio>
#include<iostream>
#include<algorithm>
#include<vector>
#include<deque>
#include<string>
#include<queue>
#include<map>
#include<set>
#include<utility>
#include<queue>

const int MAXN = 105;
using namespace std;
struct UnionFind {
  vector<int> data;
  UnionFind(int size) : data(size, -1) { }
  bool unionSet(int x, int y) {
    x = root(x); y = root(y);
    if (x != y) {
      if (data[y] < data[x]) swap(x, y);
      data[x] += data[y]; data[y] = x;
    }
    return x != y;
  }
  bool findSet(int x, int y) {
    return root(x) == root(y);
  }
  int root(int x) {
    return data[x] < 0 ? x : data[x] = root(data[x]);
  }
  int size(int x) {
    return -data[root(x)];
  }
};
struct edge{
  edge(int from,int to):from(from),to(to){}
  int from,to;
};
bool operator<(edge a,edge b){
  if(a.from != b.from)return a.from < b.from;
  else return a.to < b.to;
}
typedef pair<int,edge> P;

int main(){
  int n,m;

  while(cin >> n >> m && n + m != 0){
    priority_queue< pair<int,edge>,vector<P>,greater<P> > que;
    for (int i = 0; i < m; ++i){
      int a,b,c;
      cin >> a >> b >> c;
      que.push(make_pair(c,edge(a,b)));
    }
    UnionFind u(m);
    int cost = 0;
    for (int i = 0; i < m; ++i){
      edge top = que.top().second;
      int topCost = que.top().first;
      que.pop();
      if(u.unionSet(top.from,top.to)){
	cost += topCost;
      }
    }
    cout << cost << endl;
  }
  return 0;
}