Go: package main

import (
	"bufio"
	"fmt"
	"os"
	"strconv"
)

//util
var sc = bufio.NewScanner(os.Stdin)

func nextStr() string {
	sc.Scan()
	return sc.Text()
}

func nextInt() int {
	sc.Scan()
	i, e := strconv.Atoi(sc.Text())
	if e != nil {
		panic(e)
	}
	return i
}

func printList(list []int) {
	n := len(list)
	buf := bufio.NewWriter(os.Stdout)
	for _, v := range list[0 : n-1] {
		buf.Write([]byte(fmt.Sprintf("%d ", v)))
	}
	buf.Write([]byte(fmt.Sprintf("%d\n", list[n-1])))
	buf.Flush()
}

func max(a, b int) int {
	if a > b {
		return a
	} else {
		return b
	}
}

func min(a, b int) int {
	if a > b {
		return b
	} else {
		return a
	}
}

//solve
const (
	MAX   = 100
	INFTY = (1 << 21)
	WHITE = 0
	GRAY  = 1
	BLACK = 2
)

//V: グラフの頂点全体の集合
//T: MSTに属する頂点の集合
var (
	n     int
	M     [MAX][MAX]int //重みを記録する隣接行列
	color [MAX]int
	p     [MAX]int //MSTにおける頂点の親を記録
	d     [MAX]int //Tに属する頂点と、V−Tに属する頂点を繋ぐ辺の中で、重みが最小のものを記録
)

func prim() int {
	var u, minv int
	//初期化
	for i := 0; i < n; i++ {
		d[i] = INFTY
		p[i] = -1
		color[i] = WHITE
	}

	d[0] = 0

	for {
		//頂点uを決めていく
		//つまり、Tに属する頂点と、V−Tに属する頂点を繋ぐ辺の中で、重みが最小のものを決める
		minv = INFTY
		u = -1
		for i := 0; i < n; i++ {
			//未訪問かつ、辺の重みが最小となるuを選ぶ
			if minv > d[i] && color[i] != BLACK {
				u = i
				minv = d[i]
			}
		}

		if u == -1 {
			break
		}

		color[u] = BLACK
		for v := 0; v < n; v++ {
			//未訪問かつ、辺が存在するとき
			if color[v] != BLACK && M[u][v] != INFTY {
				if d[v] > M[u][v] {
					d[v] = M[u][v]
					p[v] = u
					color[v] = GRAY
				}
			}
		}
	}

	sum := 0
	for i := 0; i < n; i++ {
		if p[i] != -1 {
			sum += M[i][p[i]]
		}
	}
	return sum
}

func main() {
	sc.Split(bufio.ScanWords)
	n = nextInt()

	for i := 0; i < n; i++ {

		for j := 0; j < n; j++ {
			tmp := nextInt()
			if tmp == -1 {
				tmp = INFTY
			}
			M[i][j] = tmp
		}

	}

	fmt.Println(prim())

}

C++: #include <stdio.h>

int main(){
	int n, G[100][100], tree[100][99] = { 0 };
	scanf("%d", &n);
	for (int i = 0; i < n; i++){
		for (int j = 0; j < n; j++){
			scanf("%d", &G[i][j]);
		}
	}

	int min0 = 2001;
	tree[0][0]++;
	for (int i = 1; i < n; i++){
		if (G[0][i]+1 && G[0][i] < min0){
			min0 = G[0][i];
			tree[0][1] = i;
		}
	}
	tree[tree[0][1]][0]++;

	for (int connected = 2; connected < n; connected++){
		int min = 2001,mink,minl;
		for (int k = 0; k < n; k++){
			if (!tree[k][0]){
				continue;
			}
			for (int l = 0; l < n; l++){
				if (!tree[l][0] && G[k][l] + 1 && G[k][l] < min){
					min = G[k][l];
					mink = k;
					minl = l;
				}
			}
		}
		tree[mink][++tree[mink][0]] = minl;
		tree[minl][++tree[minl][0]] = mink;
	}

	int sum = 0;
	for (int i = 0; i < n; i++){
		for (int j = 0; j < tree[i][0]; j++){
			sum += G[i][tree[i][j + 1]];
		}
	}

	printf("%d\n", sum >> 1);
	return 0;
}

C++: #include<iostream>
#include<cstdio>
#include<cstring>
using namespace std;
#define INF 2000000
#define MAX 20000
int m[MAX][MAX],color[MAX],d[MAX],num;
int spaning(){
	for(int i=0;i<num;i++){
		color[i]=0;d[i]=INF;
	}
	d[0]=0;
	int sum=0;
	int min_now=INF;
	while(1){
		int v=-1;
	for(int i=0;i<num;i++){
		if(!color[i]&&(v==-1||d[v]>d[i])){
			v=i;
		}}
		if(v==-1) break;
		sum+=d[v];
		color[v]=1;
	for(int i=0;i<num;i++){
		if(!color[i]){
			d[i]=min(d[i],m[v][i]);
		}
	
	}
	}
	return sum;
}
int main(){
	int a;
	cin>>num;
	for(int i=0;i<num;i++){
		for(int j=0;j<num;j++){
			cin>>a;
			if(a==-1) m[i][j]=INF;
			else m[i][j]=a;
		}
	}
	int s=spaning(); 
	cout<<s<<endl;
}

C++: #include <iostream>
#include <queue>
#include <vector>
#include <utility>
using namespace std;
typedef pair<int,int> Info;
int main(){
        int N;
        cin >> N;
        vector <vector<int> > adjancey(N,vector<int>(N));
        priority_queue<Info, vector<Info>,greater<Info> > descending;
        for(int i=0 ; i<N ; i++ )
                for(int j=0 ; j<N ; j++ )
                        cin >> adjancey[i][j];
        Info wn;
        int now=0,counter=0;
        vector <bool> past(N,false);
        while(true){
                past[now]=true;
                for(int i=0 ; i<N ; i++ ){
                        if(past[i])
                                continue;
                        if(adjancey[now][i]==-1)
                                continue;
                        wn.first=adjancey[now][i];
                        wn.second=i;
                        descending.push(wn);
                }
                int c=0;
                for(int i=0;i<N;i++)
                        c+=past[i];
                if(c==N)break;
                wn=descending.top();descending.pop();
                now=wn.second;
                if(past[now])continue;
                counter+=wn.first;
        }
        cout << counter << endl;
        return 0;
}

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

using namespace std;

int P[110];
pair<int,int> bridge[10010];

void init(int N){
  for(int i = 0;i<N;i++){
    P[i] = i;
  }
}

int root(int a){
  if(P[a] == a){
    return a;
  }
  return(P[a] = root(P[a]));
}

bool is_same_set(int a,int b){
  return root(a) == root(b);
}

void unite(int a,int b){
  P[root(a)] = root(b);
}

int main(){
  int n,a[10010],b[10010],w,count = 0,result = 0,x,y;
  cin >>n;
  init(n);
  for(int i=0;i<n;i++){
    for(int k=0;k<n;k++){
      cin >> w;
      if(w >= 0){
        bridge[count].first = w;
        a[count] = i;
        b[count] = k;
        bridge[count].second = count;
        count ++;
      }
    }
  }
  sort(bridge,bridge+count);
  for(int i=0;i<count;i++){
    x = a[bridge[i].second];
    y = b[bridge[i].second];
    if(!is_same_set(x,y)){
      unite(x,y);
      result += bridge[i].first;
      //cout << x <<" " << y << " " << bridge[i].first << endl;
    }
  }
  cout << result << endl;
}

C++: #include <bits/stdc++.h>
#define r(i,a,n) for(int i=a;i<n;i++)
using namespace std;
int main(){
	int n,p;
	while(cin>>n>>p,n){
		int q,a[10000][1261],ch[10000][1261],b,c,d,e;
		r(i,0,p)r(j,0,1261)ch[i][j]=a[i][j]=0;
		cin>>q;
		r(i,0,q){
			cin>>b>>c>>d>>e;
			if(e==1){a[d-1][b]++;ch[d-1][b]=c;}
			else{
				for(int j=b-1;j>=0;j--){
					if(ch[d-1][j]==c)break;
					a[d-1][j]++;
				}
			}
		}
		cin>>q;
		while(q--){
			int s=0;
			cin>>b>>c>>d;
			r(i,b,c)if(a[d-1][i])s++;
			cout<<s<<endl;
		}
	}return 0;
}

C++: #include <iostream>
#include <queue>
#include <vector>
#include <utility>
using namespace std;
typedef pair<int,int> Info;
int main(){
        int N;
        cin >> N;
        vector <vector<int> > adjancey(N,vector<int>(N));
        priority_queue<Info, vector<Info>,greater<Info> > descending;
        for(int i=0 ; i<N ; i++ )
                for(int j=0 ; j<N ; j++ )
                        cin >> adjancey[i][j];
        Info wn;
        int now=0,counter=0;
        vector <bool> past(N,false);
        while(true){
                past[now]=true;
                for(int i=0 ; i<N ; i++ ){
                        if(past[i])
                                continue;
                        if(adjancey[now][i]==-1)
                                continue;
                        wn.first=adjancey[now][i];
                        wn.second=i;
                        descending.push(wn);
                }
                wn=descending.top();descending.pop();
                now=wn.second;
                if(past[now])break;
                counter+=wn.first;
        }
        cout << counter << endl;
        return 0;
}