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 <set>
#include <algorithm>

using namespace std;

int n, m;
vector< set< pair<int, int> > > cost(100,set< pair<int,int> >());

int prim()
{
	int e[100]={};
	int res=0;
	set<int> v;
	v.insert(0);
	while(v.size()<n)
	{
		for(set<int>::iterator it=v.begin();it!=v.end();it++)
		{
			for(set<  pair<int, int> >::iterator it2=cost[*it].begin();it2!=cost[*it].end();it2++)
				if(v.find((*it2).second)==v.end())
				{
					v.insert((*it2).second);
					res+=(*it2).first;
					break;
				}
		}
	}
	return res;
}

int main()
{
	while(1)
	{
		cin >> n >> m;
		if(n==0&&m==0) break;
		for(int i=0;i<m;i++)
		{
			int a, b, c;
			cin >> a >> b >> c;
			cost[a].insert(pair<int, int>(c, b));
			cost[b].insert(pair<int, int>(c, a));
		}
		cout << prim() << endl;
		for(int i=0;i<m;i++)
			cost[i].clear();
	}
	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;
priority_queue<pair<int,edge>,vector<P>,greater<P> > que;
int main(){
  int n,m;
  while(cin >> n >> m && n + m != 0){

    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 < n-1; ++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;
}

C++: #include <cstdio>
#include <cctype>
#include <utility>
#include <vector>
#include <algorithm>
using namespace std;

#define _gp(l) const auto gcu{getchar##l}; const auto pcu{putchar##l}
#ifdef __linux
_gp(_unlocked);
#else
_gp();
#endif
#define _DEF(r, n, ...) inline r n(__VA_ARGS__) noexcept
#define _T template <typename T>
#define _HT template <typename H,typename... T>
_T _DEF(T,in,int c){T n=0;int m=1;while(isspace(c)){c=gcu();}if(c=='-')m=-1,c=gcu();
	do{n=10*n+(c-'0'),c=gcu();}while(c>='0'&&c<='9');return m*n;}
_DEF(int,in,){return in<int>(gcu());}
#define _SCAN(...) _DEF(bool,scan,__VA_ARGS__)
_T _SCAN(T &n){int c=gcu();return c==EOF?n=0,false:(n=in<T>(c),true);}
_SCAN(char &c){c=gcu();gcu();return c!=EOF;}
#ifdef _GLIBCXX_STRING
_SCAN(string &s){int c;s="";
	for(;;){c=gcu();if(c=='\n'||c==' ')return true;else if(c==EOF)return false;s+=(char)c;}}
#endif
_HT _SCAN(H &h,T&&... t){return scan(h)&&scan(t...);}
#define _OUT(...) _DEF(void,out,__VA_ARGS__)
#define _OUTL(...) _DEF(void,outl,__VA_ARGS__)
_OUT(bool b){pcu('0'+b);} _OUT(const char *s){while(*s)pcu(*s++);} _OUT(char c){pcu(c);}
#ifdef _GLIBCXX_STRING
_OUT(string s){for(char c:s)pcu(c);}
#endif
_T _OUT(T n){static char b[20];char *p=b;T m=n<0?pcu('-'),-1:1;
	if(!n)*p++='0';else while(n)*p++=(char)(n%10*m+'0'),n/=10;while(p!=b)pcu(*--p);}
_OUTL(){out('\n');}
#ifdef _GLIBCXX_VECTOR
_T _OUT(vector<T> v){for(T &x:v)out(&x == &v[0]?"":" "),out(x);}
#endif
_HT _OUT(H&& h, T&&... t){out(h);out(move(t)...);}
template <typename... T> _OUTL(T&&... t){out(move(t)...);outl();}
struct range{
	int e,b=0,s=1; range(int _b,int _e,int _s):e(_e),b(_b),s(_s){} range(int _b,int _e): e(_e), b(_b){} range(int _e):e(_e){}
	struct it { int v, s; it (int _v, int _s) : v(_v), s(_s) {} operator int()const{return v;} operator int&(){return v;} int operator*()const{return v;}
		it& operator++(){v+=s;return *this;} }; it begin() {return {b, s};} it end() {return {e, s};}};

struct union_find {
	struct node {int p, r = 0;};
	vector<node> nodes;

	union_find(int n) : nodes(n) {
		int i = 0;
		for (node &n: nodes)
			n.p = i++;
	}
	int find(int x) {
		int &p = nodes[x].p;
		if (p != x)
			p = find(p);
		return p;
	}
	void unite(int a, int b) {
		int ar = find(a), br = find(b);
		node &an = nodes[ar], &bn = nodes[br];
		if (an.r > bn.r)
			bn.p = ar;
		else {
			an.p = br;
			if (an.r == bn.r)
				bn.r++;
		}
	}
	bool same(int a, int b) {
		return find(a) == find(b);
	}
};

struct edge {
	int s, t, w;
	bool operator < (edge &a) {return w < a.w;}
};

int main() {
	for (int n; (n = in());) {
		union_find V(n);
		vector<edge> E(in());
		int r = 0;
		for (edge &e: E)
			e = {in(), in(), in()};
		sort(E.begin(), E.end());
		for (edge e: E)
			if (!V.same(e.s, e.t)) {
				r += e.w;
				V.unite(e.s, e.t);
			}
		outl(r);
	}
}