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>
using namespace std;

struct UF {
  vector<int> p;
  UF(int n) : p(n,-1) {}
  int rt(int x) { return p[x]<0 ? x : p[x]=rt(p[x]); }
  bool cat(int x, int y) {
    x=rt(x); y=rt(y);
    if(x==y) return false;
    if(p[x]<p[y]) swap(x,y);
    p[y]+=p[x];
    p[x]=y;
    return true;
  }
};

int main() {
  for(int tci = 0; ; tci++) {
    int n,m; scanf("%d%d", &n, &m);
    if(n==0) break;
    vector<pair<int,pair<int,int> > > edges(m);
    for(int i = 0; i < m; i++) {
      int a,b,c; scanf("%d%d%d", &a, &b, &c);
      edges[i] = make_pair(c,make_pair(a,b));
    }
    sort(edges.begin(), edges.end());
    UF uf(n);
    long long cost_sum = 0;
    for(int i = 0; i < m; i++) {
      if(uf.cat(edges[i].second.first, edges[i].second.second)) {
        cost_sum += edges[i].first;
      }
    }
    printf("%lld\n", cost_sum);
  }
  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;
bool visited[MAXN];
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<P,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(MAXN);
    int ans = 0;
    while(!que.empty()){
      edge e = que.top().second;
      int  cost= que.top().first;
      que.pop();
      if(!u.findSet(e.from,e.to)){
	ans += cost;
	u.unionSet(e.from, e.to);
      }
    }
    cout << ans << endl;
  }
  return 0;
}

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

#define INF 2000000000

using namespace std;

int main(void){
	int n,m;
	
	while(cin >> n >> m){
		if((n|m) == 0) break;
		
		int s,t,cost;
		
		int f[n][n];
		for(int i=0;i<n;i++)for(int j=0;j<n;j++){
			f[i][j] = INF;
		}
		
		for(int i=0;i<m;i++){
			cin >> s >> t >> cost;
			f[s][t] = cost;
			f[t][s] = cost;
		}
		//Minimum Spaning Tree
		vector<int> connected;
		connected.push_back(0);
		int ret = 0;
		while(connected.size() != n){
			int mini=INF,tmp,tmpindex;
			for(int i=0;i<connected.size();i++){
				for(int j=0;j<n;j++){
					if(f[connected[i]][j] < mini && 
					find(connected.begin(),connected.end(),j) == connected.end()){
						mini = f[connected[i]][j];
						tmpindex = j;
					}
				}
			}
			ret += mini;
			connected.push_back(tmpindex);
		}
		cout << ret << endl;
	}
}

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

class union_find {
private:
	vector<int> uf;

public:
	union_find(int n):uf(n, -1){}

	inline int find(int x) {
		return uf[x] < 0 ? x : uf[x] = find(uf[x]);
	}

	inline bool unite(int x, int y) {
		x = find(x);
		y = find(y);
		if(x == y)
			return false;

		if(uf[x] > uf[y])
			swap(x, y);

		else if(uf[x] == uf[y])
			--uf[x];

		uf[y] = x;

		return true;
	}
};

typedef int weight;
struct edge {
	int u, v;
	weight cost;
	edge(int u, int v, weight c):u(u), v(v), cost(c){}

	bool operator< (const edge& o) const {
		return cost < o.cost;
	}
};

int n, m;
vector<edge> es;

weight kruskal() {
	sort(es.begin(), es.end());
	union_find uf(n);

	weight res = 0;
	for(int i = 0; i < es.size(); ++i)
		if(uf.unite(es[i].u, es[i].v))
			res += es[i].cost;

	return res;
}

int main() {
	cin.tie(0);
	ios::sync_with_stdio(false);

	while(cin >> n >> m && n) {
		es.clear();
		for(int i = 0; i < m; ++i) {
			int u, v, cost;
			cin >> u >> v >> cost;
			es.emplace_back(u, v, cost);
		}

		cout << kruskal() << endl;
	}


	return EXIT_SUCCESS;
}