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 <vector>
#include <utility>
#include <set>
#include <algorithm>
#include <utility>

using namespace std;

int map[101][100];
int n,m;

bool check(int x,vector<bool> &used){

    used[x] = true;
    bool flg = true;
    for(int i=0;i<used.size();i++){
	if(!used[i]) flg = false;
    }
    if(flg) return true;

    bool res = false;
    for(int i=0;i<n;i++){
	if(map[x][i] > 0  && !used[i]){
	    res |= check(i,used);
	}
    }

    return res;

}

int main(){

    while(true){
    cin >> n >> m;
    if(n == 0 && m == 0) break;
    vector<int> a(m);
    vector<int> b(m);
    vector<int> cost(m);
    vector< pair <  pair<int,int> , pair<int,int> > >  q(m);
    long long int sum = 0;
    for(int i=0;i<m;i++){
	cin >> a[i] >> b[i] >> cost[i];
	sum += cost[i];
	q[i] = pair< pair<int,int>, pair<int,int> >(pair<int,int>(cost[i],a[i]), pair<int,int>(b[i],i));
	map[a[i]][b[i]] = cost[i];
	map[b[i]][a[i]] = cost[i];
    }
    sort(q.rbegin(),q.rend());
    for(int i=0;i<m;i++){
	int x = q[i].first.second ;
	int y = q[i].second.first ;
	int temp = map[x][y];
	map[x][y]  = 0;
	map[y][x]  = 0;
	vector<bool> used1(n,false);
	vector<bool> used2(n,false);
	if(check(x,used1) && check(y,used2)){
	    sum -= temp;
	}else{
	    map[x][y]  = temp;
	    map[y][x]  = temp;
	}
    }
    cout << sum << endl;
    }

    return 0;
}

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

using namespace std;

struct Edge {
	int a, b, cost;
};

int n, m;
int root[100], high[100];
Edge e[100000];

void init(int n) {
	for (int i = 0; i < n; i++)root[i] = i, high[i] = 1;
}

int getroot(int n){
	if (n == root[n])return n;
	return root[n] = getroot(root[n]);
}

bool issame(int a, int b) {
	return getroot(a) == getroot(b);
}

void unite(int a, int b) {
	a = getroot(a), b = getroot(b);
	if (a == b)return;
	if (high[a] > high[b])root[b] = a;
	else if (high[a] < high[b])root[a] = b;
	else if (high[a] == high[b])root[a] = b, high[a]++;
}

int main() {
	while (cin >> n >> m, n + m) {
		for (int i = 0; i < m; i++) {
			cin >> e[i].a >> e[i].b >> e[i].cost;
		}
		sort(e, e + m, [](Edge& l, Edge& r) {
			return l.cost < r.cost;
		});
		int ans = 0;
		init(n);
		for (int i = 0; i < m; i++) {
			if (!issame(e[i].a, e[i].b)) {
				unite(e[i].a, e[i].b);
				ans += e[i].cost;
			}
		}
		cout << ans << endl;
	}
	return 0;
}

C++: #include<stdio.h>
#include<string.h>
#include<math.h>
int main(void)
{
	int a,s,d[101],f[101],g[101],h,i,j,size[101],ban[101];
	int z,x,q;
	while(1){
		q=0;
		scanf("%d %d",&a,&s);
		if(a==0&&s==0) break;
		for(i=0;i<a;i++){
			ban[i]=i;
			size[i]=1;
		}
		for(i=0;i<s;i++) scanf("%d %d %d",&d[i],&f[i],&g[i]);
		for(i=0;i<s;i++){
			if(d[i]>f[i]) h=d[i]; d[i]=f[i]; f[i]=h;
			for(j=i+1;j<s;j++){
				if(g[i]>g[j]){
					h=g[i]; g[i]=g[j]; g[j]=h;
					h=d[i]; d[i]=d[j]; d[j]=h;
					h=f[i]; f[i]=f[j]; f[j]=h;
				}
			}
		}
		for(i=0;i<s;i++){
			z=d[i]; x=f[i];
			while(ban[z]!=z) z=ban[z];
			while(ban[x]!=x) x=ban[x];
			if(z!=x){
				q+=g[i];
				if(size[x]>size[z]) ban[z]=x;
				else if(size[x]<size[z]) ban[x]=z;
				else{
					ban[x]=z;
					size[x]++;
				}
			}
		}
		printf("%d\n",q);
	}
	return 0;
}

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

typedef int Weight;
struct Edge {  
  int src, dst;
  Weight weight;
  Edge(int src, int dst, Weight weight) :
    src(src), dst(dst), weight(weight) { }
};
bool operator < (const Edge &e, const Edge &f) {
  return e.weight != f.weight ? e.weight > f.weight : 
    (e.src != f.src ? e.src < f.src : e.dst < f.dst);
}
typedef vector<Edge> Edges;
typedef vector<Edges> Graph;

pair<Weight, Edges> prim(const Graph &g, int r = 0) {
  int n = g.size();
  Edges T;
  Weight total = 0;
  vector<bool> visited(n);
  priority_queue<Edge> Q;
  Q.push( Edge(-1, r, 0) );    
  while (!Q.empty()) {
    Edge e = Q.top(); Q.pop();
    if (visited[e.dst]) continue;
    T.push_back(e);
    total += e.weight;
    visited[e.dst] = true;
    for(auto f : g[e.dst]){
        if(!visited[f.dst]) Q.push(f);
    }
  }
  T.erase(T.begin());
  return pair<Weight, Edges>(total, T);
}

int main(){
    while(1){
        int n, m; cin >> n >> m;
        if(n==0) break;
        Graph g(n);
        int a, b, cost;
        for(int i=0; i<m; i++){
            cin >> a >> b >> cost;
            g[a].push_back(Edge(a, b, cost));
            g[b].push_back(Edge(b, a, cost));
        }

        cout << prim(g).first << endl;
    }
}