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 <queue>
#include <vector>
#include <functional>

using namespace std;

class Bridge
{
public:
	int from;
	int to;
	int cost;

	Bridge() : from(0), to(0), cost(0) {}

	bool operator > (const Bridge& b) const
	{
		return cost > b.cost;
	}

	bool operator < (const Bridge& b) const
	{
		return cost < b.cost;
	}
};



int nCity, nBridge;

Bridge bridge[100];
bool city[100];

int main()
{
	while( 1 )
	{
		//load data
		cin >> nCity >> nBridge;
		if(nCity == 0 && nBridge == 0)
		{
			break;
		}

		for(int i=0; i<nBridge; i++)
		{
			cin >> bridge[i].from >> bridge[i].to >> bridge[i].cost;
		}

		for(int i=0; i<nCity; i++)
		{
			city[i] = false;
		}

		//set initial node to queue
		priority_queue<Bridge, vector<Bridge>, greater<Bridge> > que;
		for(int i=0; i<nBridge; i++)
		{
			if(bridge[i].from == 0 || bridge[i].to == 0)
			{
				que.push(bridge[i]);
			}
		}

		city[0] = true;

		//iteration
		int totalCost = 0;
		while(!que.empty())
		{
			//end check
			bool isEnd = true;
			for(int i=0; i<nCity; i++)
			{
				if(!city[i])
				{
					isEnd = false;
					break;
				}
			}

			if(isEnd)
			{
				break;
			}

			//check highest priority node
			Bridge current = que.top();
			que.pop();

			totalCost += current.cost;

			break;

			int next = 0;
			if(!city[current.to])
			{
				city[current.to] = true;
				next = current.to;
			}
		
			if(!city[current.from])
			{
				city[current.from] = true;
				next = current.from;
			}

			for(int i=0; i<nBridge; i++)
			{
				if((bridge[i].to == next && !city[bridge[i].from]) || 
				   (bridge[i].from == next && !city[bridge[i].to]))
				{
					que.push(bridge[i]);
				}
			}
		}

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

C++: #include <bits/stdc++.h>
using namespace std;

const int INF = 1<<29;

const int MAX_N = 100, MAX_M = 100;

int n, m;
int G[MAX_N][MAX_N];
int d[MAX_N];
bool visited[MAX_N];

int main(){
    while(scanf("%d%d", &n, &m) && (n||m)){
        for(int x = 0; x < n; x++){
            for(int y = 0; y < n; y++){
                if(x - y) G[x][y] = INF;
                else G[x][y] = 0;
            }
        }
        for(int x = 0; x < m; x++){
            int a, b, c;
            scanf("%d%d%d", &a, &b, &c);
            G[a][b] = c;
            G[b][a] = c;
        }
        fill(d, d+n, INF);
        fill(visited, visited+n, false);
        d[0] = 0;
        visited[0] = true;
        int ans = 0;
        int a = 0;
        for(int x = 0; x < n; x++){
            int v = -1;
            for(int y = 0; y < n; y++){
                if(visited[y]) continue;
                d[y] = min(d[y], G[a][y]);
                if(v == -1 || d[y] < d[v]){
                    v = y;
                }
            }
            if(v == -1) break;
            visited[v] = true;
            ans += d[v];
            a = v;
        }
        printf("%d\n", ans);
    }
    return 0;
}

C++: #include<iostream>
#include<string>
#include<algorithm>
#include<stack>
#include<queue>
#include<vector>
#include<cstdio>
#include<cstring>
#include<cmath>
using namespace std;

#define rep(i,n) for(int i=0;i<n;i++)
#define REP(n) rep(i,n)

typedef pair<int,int> pp;

const int maxn = 110, inf = 10100;

int cost[maxn][maxn];
bool used[maxn];
int n,m,a,b;

int main()
{
	while(cin >> n >> m && (n && m))
	{
		memset(used, false, sizeof(used));
		memset(cost,inf, sizeof(cost));
		priority_queue<pp, vector<pp>, greater<pp> > que;
		que.push(pp(0, 0));

		int ans = 0;
		REP(m)
		{
			cin >> a >> b;
			cin >> cost[a][b];
			cost[b][a] = cost[a][b];
		}
		
		while(!que.empty())
		{
			pp p = que.top(); que.pop();
			if(used[p.second]) continue;
			
			ans += p.first;
			used[p.second] = true;
			
			REP(n) que.push(pp(cost[p.second][i], i ));
		}
		cout << ans << endl;
	}

	return 0;
}

C++: #include <stdio.h>
#include <vector>
#include <algorithm>

struct union_find {
	std::vector<int> data;

public:
	union_find(int n) : data(n, -1) {}
	bool unite(int x, int y) {
		x = find(x); y = find(y);
		if(x == y) return false;
		if(data[x] > data[y]) std::swap(x, y);
		data[x] += data[y];
		data[y] = x;
		return true;
	}
	int find(int k) {
		if(data[k] < 0) return k;
		return data[k] = find(data[k]);
	}
};

int main() {
	using P = std::pair<int, std::pair<int, int>>;

	int n, m;
	while(scanf("%d%d", &n, &m), n) {
		int ans = 0;
		std::vector<P> vec;
		for(int i = 0; i < m; i++) {
			int a, b, c; scanf("%d%d%d", &a, &b, &c);

			vec.push_back({c, {a, b}});
		}
		sort(begin(vec), end(vec));
		
		union_find uf(n);
		for(auto v: vec) {
			if(uf.unite(v.second.first, v.second.second)) ans += v.first;
		}
		printf("%d\n", ans);
	}
	return 0;
}