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 <map>
#include <vector>
#include <algorithm>
#include <numeric>

using namespace std;

int data[101][101];

int prim( int n )
{
	vector<int> key( n, 9999999 );
	key[0] = 0;
	map<int,int> pq;
	bool inQueue[101];
	for( int i = 0;i < 101;i++ ) inQueue[i] = true;
	for( int i = 0;i < n;i++ ){
		pq.insert( pair<int,int>( i, key[i] ) );
	}

	while( !pq.empty() ){
		map<int,int>::iterator target = pq.begin();
		for( map<int,int>::iterator it = pq.begin();it != pq.end();it++ ){
			if( target->second > it->second ) target = it;
		}
		int u = target->first;
		pq.erase( target );
		inQueue[u] = false;

		for( int i = 0;i < n;i++ ){
			if( data[u][i] ){
				if( inQueue[i] ){
					int w = data[u][i];
					if( w < key[i] ){
						key[i] = w;
						pq[i] = w;
					}
				}
			}
		}
	}

	int answer = 0;
	for( int i = 0;i < n;i++ ){
		answer += key[i];
	}

	return answer;
}

int main(int argc, char const* argv[])
{
	int n,m;
	int a,b,cost;

	while( cin >> n >> m && n != 0 ){
		for( int i = 0;i < 101;i++ ){
			for( int j = 0;j < 101;j++ ){
				data[i][j] = 0;
			}
		}
		for( int i = 0;i < m;i++ ){
			cin >> a >> b >> cost;
			data[a][b] = cost;
			data[b][a] = cost;
		}

		int answer = prim( n );
		cout << answer << endl;
	}

	return 0;
}

C++: #include <iostream>
#define TOSHI_MAX 100
#define COST_MAX 100000
using namespace std;

int prim(int data[][TOSHI_MAX], int toshiNum) {
  bool visited[toshiNum];
  int cost[toshiNum];
  for(int i = 0; i < toshiNum; i++) {
    visited[i] = false;
    cost[i] = COST_MAX;
  }
  cost[0] = 0;
  while(1) {
    int min = COST_MAX;
    int p;
    for(int i = 0; i < toshiNum; i++) {
      if(!visited[i] && cost[i] < min) {
	min = cost[i];
	p = i;
      }
    }
    if(min == COST_MAX) break;

    visited[p] = true;
    for(int i = 0; i < toshiNum; i++) {
      if(!visited[i] && data[p][i] < cost[i]) {
	cost[i] = data[p][i];
      }
    }
  }

  int ans = 0;
  for(int i = 0; i < toshiNum; i++) {
    if(cost[i] != COST_MAX) ans += cost[i];
  }

  return ans;
}

int main() {
  while(1) {
    int n, m;
    cin >> n >> m;
    if(n == 0 && m == 0) break;

    int data[TOSHI_MAX][TOSHI_MAX];
    for(int i = 0; i < n; i++) {
      for(int j = 0; j < m; j++) {
	data[i][j] = COST_MAX;
      }
    }

    for(int i = 0; i < m; i++) {
      int a, b, cost;
      cin >> a >> b >> cost;
      data[a][b] = data[b][a] = cost;
    }

    cout << prim(data, m) << endl;
  }

  return 0;
}

C++: #include <iostream>
#incldue <cstdio>
#define rep(i,n) for(int i=0;i<n;i++)
//#define int long long
using namespace std;

#define INF 999999

int n, m;
int a, b, c;

int cost[100][100];
int mincost[100];
bool used[100];

void init()
{
	rep(i,100) rep(j,100)
	{
		cost[i][j] = INF;
	}
}

int prim()
{
	rep(i,n)
	{
		mincost[i] = INF;
		used[i] = false;
	}

	mincost[0] = 0;
	int res = 0;

	while (true)
	{
		int v = -1;
		rep(u,n)
		{
			if (!used[u] && (v == -1 || mincost[u] < mincost[v])) v = u;
		}

		if (v == -1) break;
		used[v] = true;
		res += mincost[v];

		rep(u,n)
		{
			mincost[u] = min(mincost[u], cost[v][u]);
		}
	}

	return res;
}

int main()
{
	while (true)
	{
		cin >> n >> m;
		if (n == 0 && m == 0) break;

		init();

		rep(i,m)
		{
			cin >> a >> b >> c;
			cost[a][b] = c;
			cost[b][a] = c;
		}

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

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

struct edge{int u,v,cost;};

int par[101],rank[101];
edge es[200];
int V,E;

void init_union_find(int);
int find(int);
void unite(int,int);
bool same(int,int);
bool comp(const edge& e1,const edge& e2);
int kruskal(void);

using namespace std;

int main(void){
  int i,a,b,c;

  while(cin >> V >> E && V){
    for(i=0;i<E;i++){
      cin >> a >> b >> c;
      es[i].u=a;
      es[i].v=b;
      es[i].cost=c;
    }
    printf("%d\n",kruskal());
  }
  return 0;
}

void init_union_find(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);
}

bool comp(const edge& e1,const edge& e2){
  return e1.cost < e2.cost;
}

int kruskal(){
  sort(es,es+E,comp);
  init_union_find(V);
  int res=0;
  for(int i=0;i<E;i++){
    edge e=es[i];
    if(!same(e.u,e.v)){
      unite(e.u,e.v);
      res+=e.cost;
    }
  }
  return res;
}