Go: package main

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

// I/O
type Scanner struct {
	sc *bufio.Scanner
}

func NewScanner() *Scanner {
	sc := bufio.NewScanner(os.Stdin)
	sc.Split(bufio.ScanWords)
	sc.Buffer(make([]byte, 1024), int(1e+9))
	return &Scanner{sc}
}

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

func (s *Scanner) nextInt() int {
	i, e := strconv.Atoi(s.nextStr())
	if e != nil {
		panic(e)
	}
	return i
}

func (s *Scanner) nextFloat() float64 {
	f, e := strconv.ParseFloat(s.nextStr(), 64)
	if e != nil {
		panic(e)
	}
	return f
}

func (s *Scanner) nextRuneSlice() []rune {
	return []rune(s.nextStr())
}

func (s *Scanner) nextIntSlice(n int) []int {
	res := make([]int, n)
	for i := 0; i < n; i++ {
		res[i] = s.nextInt()
	}
	return res
}

func (s *Scanner) nextFloatSlice(n int) []float64 {
	res := make([]float64, n)
	for i := 0; i < n; i++ {
		res[i] = s.nextFloat()
	}
	return res
}

// Arithmetic
func max(nums ...int) int {
	m := nums[0]
	for _, i := range nums {
		if m < i {
			m = i
		}
	}
	return m
}

func min(nums ...int) int {
	m := nums[0]
	for _, i := range nums {
		if m > i {
			m = i
		}
	}
	return m
}

func abs(x int) int {
	if x > 0 {
		return x
	}
	return -x
}

func pow(x, y int) int {
	res := 1
	for i := 0; i < y; i++ {
		res *= x
	}
	return res
}

func ceil(a, b int) int {
	if a%b == 0 {
		return a / b
	} else {
		return a/b + 1
	}
}

// Sort
type RuneSlice []rune

func (a RuneSlice) Len() int           { return len(a) }
func (a RuneSlice) Less(i, j int) bool { return a[i] < a[j] }
func (a RuneSlice) Swap(i, j int)      { a[i], a[j] = a[j], a[i] }

const INF = 1 << 60

// Main
func main() {
	sc := NewScanner()
	wtr := bufio.NewWriter(os.Stdout)
	N := sc.nextInt()
	G := make([][]int, N)
	for i := 0; i < N; i++ {
		G[i] = make([]int, N)
		for j := 0; j < N; j++ {
			G[i][j] = sc.nextInt()
		}
	}
	d := make([]int, N)
	for i := 0; i < N; i++ {
		d[i] = INF
	}
	seen := make([]bool, N)
	d[0] = 0
	ans := 0
	for {
		cur := 0
		minCost := INF
		for i := 0; i < N; i++ {
			if !seen[i] && d[i] < minCost {
				minCost = d[i]
				cur = i
			}
		}
		if minCost == INF {
			break
		}
		seen[cur] = true
		ans += d[cur]
		for i := 0; i < N; i++ {
			cost := G[cur][i]
			if cost != -1 && cost < d[i] {
				d[i] = cost
			}
		}
	}

	fmt.Fprintln(wtr, ans)
	wtr.Flush()
}

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;
}

C++: #include<iostream>
#include<cstring>
#include<algorithm>
using namespace std;

#define INF 2000000000

int x[10000][10000];
int MIN[10000];
int p[10000];

int prim(){
    int v,MINX;
    int col[10000];
    for(int i=0;i<n;i++){
        MIN[i]=INF;
        p[i]=-1;
        col[i]=0;
    }
    MIN[0]=0;
    while(true){
        MINX=INF;
        v=-1;
        for(int i=0;i<n;i++){
            if(MINX > MIN[i] && col != 2){
                u=i;
                MINX = MIN[i];
            }
        }
        if(u==-1){
            break;
        }
        color[u]=black;
        for(int k=0;k<n;k++){
            if(color != 0 && x[u][k]!=-1 && MIN[k]>x[u][k]){
                MIN[k]=x[u][k];
                col[k]=1;
            }
        }
    }
    int sum=0;
    for(int i=0;i<n;i++){
        sum += x[i][MIN[i]];
    }
    return sum;
}

int main() {
	int n, a;
	cin >> n;
	for (int i = 0; i < n; i++) {
		for (int j = 0; j < n; j++) {
			cin >> a;
			x[i][j] = a;
		}
	}
    cout<<prim()<<endl;
	return 0;
}