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 <vector>
#include <queue>
#include <functional>
#include <string.h>

using namespace std;
typedef pair<int, int> P;
struct edge
{
	int to;
	int cost;
};

vector<edge> G[101];
bool isUsed[101];

void solve()
{
	int n;
	cin >> n;
	vector< vector<int> > data((n), vector<int>(n));
	for (int i = 0; i < n; ++i)
	{
		for (int j = 0; j < n; ++j)
		{
			int c;
			cin >> data[i][j];
		}
	}
	for (int i = 0; i < n; ++i)
	{
		for (int j = i; j < n; ++j)
		{
			if (data[i][j] != -1)
			{
				edge e1, e2;
				e1.to = j;
				e1.cost = data[i][j];
				e2.to = i;
				e2.cost = data[j][i];
				G[i].push_back(e1);
				G[j].push_back(e2);
			}
		}
	}
	memset(isUsed, 0, sizeof(isUsed));
	int ans = 0;
	priority_queue < P, vector<P>, greater<P> > pque;
	pque.push(P(0, 0));
	while (!pque.empty())
	{
		P p = pque.top();
		pque.pop();
		int v = p.second;
		if (isUsed[v])
		{
			continue;
		}
		isUsed[v] = true;
		ans += p.first;
		for (int i = 0; i < G[v].size(); ++i)
		{
			edge e = G[v][i];
			pque.push(P(e.cost, e.to));
		}
	}
	cout << ans << endl;
}

int main()
{
	solve();
	return(0);
}

C++: #include<iostream>
using namespace std;
static const int MAX = 100;
static const int INFTY = (1<<21);
static const int WHITE = 0;
static const int GRAY = 1;
static const int BLACK = 2;

struct Node{
  int color, parent;
};

int n, M[MAX][MAX];
Node node[MAX];

void Printnodes(){
  string col[3] = {"WHITE", "GRAY ", "BLACK"};
  for(int i = 0; i < n; i++){
    cout << "nodeID : " << i ;
    cout << " color : " << col[node[i].color];
    cout << " parent : " << node[i].parent << endl;
  }
  cout << endl;
}

int main(){
  cin >> n;

  for(int i = 0; i < n; i++){
    for(int j = 0; j < n; j++){
      cin >> M[i][j];
    }
    node[i].color = WHITE;
    node[i].parent = -1;
  }

  node[0].color = BLACK;
  int totaldist = 0;

  while(true){
    Printnodes();

    int count = 0, min_d = INFTY, min_id, dist;
    for(int p = 0; p < n; p++){
      if(node[p].color == BLACK){
        for(int i = 0; i < n; i++){
          if(M[p][i] > 0 && node[i].color != BLACK){
            count++;
            node[i].color = GRAY;
            dist = M[p][i];
            if(dist < min_d){
              min_d = dist;
              min_id = i;
              node[i].parent = p;
            }
          }
        }
      }
    }

    if(count == 0)
      break;
    node[min_id].color = BLACK;
    totaldist += min_d;
  }

  cout << totaldist << endl;
  return 0;
}

C++: #include <stdio.h>
using namespace std;
static const int MAX = 100;
static const int INFTY = (1<<21);
static const int WHITE = 0;
static const int GRAY = 0;
static const int BLACK = 0;

int n, M[MAX][MAX];

int prim() {
    int d[n], p[n];
    int color[n];
    
    for(int i=0; i<n; i++) {
        color[i] = WHITE;
        d[i] = INFTY;
    }
    d[0] = 0;
    p[0] = -1;
    
    int sum = 0;
    
    while(1) {
        int u;
        int mincost = INFTY;
        for (int i=0; i<n; i++) {
            if (color[i] != BLACK && d[i] < mincost) {
                mincost = d[i];
                u = i;
            }
        }
        
        if (mincost == INFTY) break;
        
        color[u] = BLACK;
        
        int tmp=0;
        for (int v=0; v<=n; v++) {
            if (color[v] != BLACK && M[u][v] != -1) {
                if(M[u][v] < d[v]) {
                    d[v] = M[u][v];
                    p[v] = u;
                    color[v] = GRAY;
                    tmp = d[v];
                }
            }
        }
        sum += tmp;
    }

    return sum;
}

int main() {
    scanf("%d", &n);
    for (int i=0; i<n; i++) {
        for (int j=0; j<n; j++) {
            scanf("%d", &M[i][j]);
        }
    }
    
    int sum = prim();
    printf("%d\n", sum);
    
    return 0;
}

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

int A[101][101];
char type[101];
int p[101];//親
int d[101];//重み
int n;
int dsum = 0;

int Prim(int k){
    type[k] = 'B';
    //cout << "now in " << k << endl;;
    for(int i=1; i<=n; i++){
        if((A[k][i] != -1) && (type[i] != 'B')){
            if(A[k][i] < d[i]){
                d[i] = A[k][i];
                type[i] = 'G';
                //cout << "d[" << i << "] is " << d[i] << endl;
            }
        }
    }
    int min = 0;
    for(int j=1; j<=n; j++){
        if(type[j] == 'G'){
            if(d[j] < d[min]){
                min = j;
            }
        }
    }
    if(min == 0){
        return 0;
    } else {
        dsum += d[min];
        Prim(min);
    }
}

int main(){
    cin >> n;
    for(int i=1; i<=n; i++){//データを代入
        for(int j=1; j<=n; j++){
            cin >> A[i][j];
        }
    }

    //p,d,typeの初期化
    for(int i=0; i<=n; i++){
        type[i] = 'W';
        d[i] = 2001;
    }

    Prim(1);

    cout << dsum << endl;
}

C++: #include <cstdio>
#include <vector>

int main(void){
	int n, min_edge, next_node, count, sum;
	scanf("%d", &n);
	std::vector< std::vector<int> > edges;
	std::vector<int> isUsed;
	edges.resize(n);
	isUsed.resize(n);
	for(int i=0;i<n;i++){
		isUsed[i]=-1;
		edges[i].resize(n);
		for(int j=0;j<n;j++){
			scanf("%d", &edges[i][j]);
		}
	}

	min_edge=3000;
	isUsed[0] = 1;
	count = 0;
	sum=0;
	while(count<n-1){
		for(int i=0;i<n;i++){
			if(isUsed[i]==1){
				for(int j=0;j<n;j++){
					if (isUsed[j]==-1 && edges[i][j]>-1 && edges[i][j]<min_edge){
						min_edge = edges[i][j];
						next_node = j;
					}
				}
			}
		}
		sum += min_edge;
		isUsed[next_node]=1;
		min_edge = 3000;
		count += 1;
	}
	printf("%d\n", sum);
	return 0;
}