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<cstdio>
#include<algorithm>
#include<queue>
#include<cstring>
#include<cstdlib>
#include<vector>
#define MAX_V 1000
#define INF 1<<29
#define cl(a,b) for(int i=0;i<a;i++)for(int j=0;j<b;j++)cost[i][j] = INF;
#define de(a)  for(int i=0;i<a;i++){cout << mincost[i] << " "; if(i == a-1){cout << endl;}}
#define de2(a,b) for(int I=0;I<a;I++){for(int j=0;j<b;j++){cout << cost[I][j] << " ";}cout << endl;}cout << endl;
using namespace std;

int cost[MAX_V][MAX_V];
int mincost[MAX_V];
bool used[MAX_V];
int V;
 bool connect[10000];

int prime()
{
  for(int i=0;i<V;++i)
    {
      mincost[i]=INF;
      used[i]=false;
    }

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

  //de(10);
  

  //de2(10,10);
  

  while(true)
    {
      int v = -1; 
      for(int u = 0; u<V ; u++ )
	{
	  if(connect[u] && !used[u] && (v == -1 || mincost[u] < mincost[v]))
	    {
	      v = u;
	    }
	}

      if(v == -1)break;
      used[v] = true;
      res += mincost[v];
     
      for(int u = 0; u < V; u++)
	{
	 
	  mincost[u] = min(mincost[u],cost[v][u]);
	  //cout << "mincost[u] = " << mincost[u] << ", cost[v][u] = " << cost[v][u] << endl;
	  
	}
    }
  return res;
}



int main()
{

  int n,m,a,b;
 

  while(true)
    {
      cin >> n >> m;
      if(n == 0 && m == 0)break;
      cl(n,n);
      memset(connect,false,sizeof(connect));

      V = n;
      for(int i=0;i<m;i++)
	{
	  cin >> a >> b;
	  cin >> cost[a][b];
	  cost[b][a] = cost[a][b];
	  connect[a] = true;
	  connect[b] = true;
	}
      

      cout << prime() << endl;




    }

}

C++: #include <cstdio>
#include <vector>
#include <utility>
using namespace std;
#define INF (1<<30)

int n,m;
bool linked[100] = {false};
vector<vector<pair<int,int> > > vec;

int main(){
	while(scanf("%d%d",&n,&m), n != 0){
		vec = vector<vector<pair<int,int> > >(n);
		for(int i = 0; i < m; i++){
			int a,b,cost;
			scanf("%d%d%d",&a,&b,&cost);
			vec[a].push_back(make_pair(b,cost));
			vec[b].push_back(make_pair(a,cost));
		}
		for(int i = 0; i < n; i++){
			linked[i] = false;
		}
		linked[0] = true;

		int ans = 0;
		for(int i = 1; i < n; i++){
			int mi = INF;
			int mic = INF;
			for(int j = 0; j < n; j++){
				if(linked[j]){
					int mj = INF;
					int mjc = INF;
					for(int k = 0; k < vec[j].size(); k++){
						if(vec[j][k].second < mjc && !linked[vec[j][k].first]){
							mj = vec[j][k].first;
							mjc = vec[j][k].second;
						}
					}
					if(mjc < mic){
						mi = mj;
						mic = mjc;
					}
				}
			}
			ans += mic;
			linked[mi] = true;
		}
		printf("%d\n",ans);
	}
	return 0;
}

C++: //Name: Stellar Performance of the Debunkey Family
//Level: 2
//Category: グラフ,Graph,最小全域木,Minimum Spanning Tree,MST
//Note:

/*
 * 最小全域木を求めればよい。
 *
 * このコードではKruskal法を用いている。
 * オーダーは O(M log M)。
 */
#include <iostream>
#include <algorithm>
#include <vector>

using namespace std;

struct Edge {
    int a, b, c;

    bool operator <(const Edge &e) const {
        return c < e.c;
    }
};

struct DisjointSet/*{{{*/
{
  vector<int> parent;

  int root(int x)
  {
    if (parent[x] < 0) {
      return x;
    } else {
      parent[x] = root(parent[x]);
      return parent[x];
    }
  }

  explicit DisjointSet(int n) : parent(n, -1) {}

  bool unite(int x, int y)
  {
    const int a = root(x);
    const int b = root(y);
    if (a != b) {
      if (parent[a] < parent[b]) {
        parent[a] += parent[b];
        parent[b] = a;
      } else {
        parent[b] += parent[a];
        parent[a] = b;
      }
      return true;
    } else {
      return false;
    }
  }

  bool find(int x, int y) { return root(x) == root(y); }
  int size(int x) { return -parent[root(x)]; }
};/*}}}*/

bool solve() {
    int N, M;
    if(!(cin >> N >> M)) return false;
    if(!N && !M) return false;

    vector<Edge> edges(M);
    for(int i = 0; i < M; ++i) {
        Edge &e = edges[i];
        cin >> e.a >> e.b >> e.c;
    }
    sort(begin(edges), end(edges));

    DisjointSet ds(N);
    int ans = 0;
    for(const auto &e : edges) {
        if(ds.unite(e.a, e.b)) {
            ans += e.c;
        }
    }
    cout << ans << endl;
    return true;
}

int main() {
    cin.tie(0);
    ios::sync_with_stdio(0);
    
    while(solve()) ;
    return 0;
}