Go: package main

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

const BIG_COST = 3000

const (
	ST_NOT_YET = iota
	ST_JOINED
)

func main() {
	sc := bufio.NewScanner(os.Stdin)
	sc.Split(bufio.ScanWords)

	nNodes := scanInt(sc)
	costs := make([][]int, nNodes)

	for r := 0; r < nNodes; r++ {
		costs[r] = make([]int, nNodes)
		for c := 0; c < nNodes; c++ {
			costs[r][c] = scanInt(sc)
		}
	}

	states := make([]int, nNodes)
	minCosts := make([]int, nNodes)

	for i := 1; i < nNodes; i++ {
		minCosts[i] = BIG_COST
	}

	for {
		var u int
		minCost := BIG_COST

		for i := 0; i < nNodes; i++ {
			if states[i] != ST_JOINED && minCosts[i] < minCost {
				minCost = minCosts[i]
				u = i
			}
		}

		// 全てのノードが MST に JOIN できたので終了。
		if minCost == BIG_COST {
			break
		}

		states[u] = ST_JOINED

		for v := 0; v < nNodes; v++ {
			cost := costs[u][v]

			// MST内の u と MST外の v との辺の重みをそれぞれ minCosts[v] として
			// 保存しておく。このうち辺の重みが最小となる v が次のループで MST に JOIN する。
			if states[v] != ST_JOINED && cost != -1 && cost < minCosts[v] {
				minCosts[v] = cost
			}
		}
	}

	sum := 0
	for _, cost := range minCosts {
		sum += cost
	}
	fmt.Println(sum)
}

func scanInt(sc *bufio.Scanner) int {
	sc.Scan()
	v, _ := strconv.Atoi(sc.Text())
	return v
}

C++: #include <iostream>
#define MAX 100
#define INF (1<<21)
#define WHITE 0
#define GRAY 1
#define BLACK 2
using namespace std;

int M[MAX][MAX],n;
int prim(){
	int u,minv;
	int d[MAX],p[MAX],color[MAX];
	for(int i = 0;i < n;i++){
		d[i] = INF;
		p[i] = -1;
		color[i] = WHITE;
	}

	d[0] = 0;

	while(1){
		minv = INF;
		u = -1;
		for(int i = 0;i < n;i++){
			if(minv > d[i] && color[i] != BLACK){
				u = i;
				minv = d[i];
			}
		}
		if(u == -1)break;
		color[u] = BLACK;
		for(int v = 0;v < n;v++){
			if(color[v] != BLACK && M[u][v] != INF){
				if(d[v] > M[u][v]){
					d[v] = M[u][v];
					p[v] = u;
					color[v] = GRAY;
				}
			}
		}
	}
	int sum = 0;
	for(int i = 0;i < n;i++){
		if(p[i] != -1)sum += M[i][p[i]];
	}

	return sum;

}


int main(){
	int e;
	cin >> n;
	for(int i = 0;i < n;i++){
		for(int j = 0;j < n;j++){
			cin >> e;
			if(e == -1)M[i][j] = INF;
			else M[i][j] = e;
		}
	}

	cout << prim() <<endl;
	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;

int n, M[MAX][MAX];

int prim(){
    int u, minv;
    int d[MAX], p[MAX], color[MAX];

    for(int i=0; i<n; i++){
        d[i] = INFTY;
        p[i] = -1;
        color[i] = WHITE;
    }

    d[0] = 0;

    while(1){
        minv = INFTY;
        u = -1;
        for(int i=0; i<n; i++){
            if(minv > d[i] && color[i] != BLACK){
                u = i;
                minv = d[i];
            }
        }
        if(u == -1) break;
        color[u] = BLACK;
        for(int v=0; v<n; v++){
            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;
                }
            }
        }
    }
    int sum = 0;
    for(int i=0; i<n; i++){
        if(p[i] != -1) sum += M[i][p[i]]; //辺の重みの総和を計算
    }

    return sum;
}

int main(){
    cin >> n;

    for(int i=0; i<n; i++){
        for(int j=0; j<n; j++){
            int e; cin >> e;
            M[i][j] = (e == -1) ? INFTY : e;
        }
    }

    cout << prim() << endl;

    return 0;
}

C++: import java.util.Scanner;

class Main
{
    static int[][]M = new int[100][100];

    static int prim(int n)
    {
	int u, minv;
	int sum = 0;
	int[]d = new int[100];
	int[]f = new int[100];
	int[]cl = new int[100];

	for(int i = 0; i < n; i++)
	    {
		d[i] = 200000;
		f[i] = -1;
		cl[i] = 0;
	    }

	d[0] = 0;

	while(true)
	    {
		minv = 200000;
		u = -1;

		for(int i = 0; i < n; i++)
		    {
			if(minv > d[i] && cl[i] != 2)
			    {
				u = i;
				minv = d[i];
			    }
		    }

		if(u == -1) break;
		cl[u] = 2;

		for(int j = 0; j < n; j++)
		    {
			if(cl[j] != 2 && M[u][j] != 200000)
			    {
				if(d[j] > M[u][j])
				   {
				       d[j] = M[u][j];
				       f[j] = u;
				       cl[j] = 1;
				   }
			    }
		    }
	    }
		for(int i = 0; i < n; i++)
		    {
			if(f[i] != -1) sum += M[i][f[i]];
		    }
	    
	return sum;
    }

    public static void main(String[] args)
    {
	Scanner In = new Scanner(System.in);

	int n = In.nextInt();

	for(int i = 0; i < n; i++)
	    {
		for(int j = 0; j < n; j++)
		    {
			int e = In.nextInt();
			M[i][j] = ((e == -1) ? 200000 : e);
		    }
	    }

	System.out.println(prim(n));

    }
}

C++: #include <bits/stdc++.h>
#define P pair<int,int>
using namespace std;

int a[100][100];
bool used[100];
signed main(){
	int b; cin >> b;
	for (int c = 0; c < b; c++) {
		for (int d = 0; d < b; d++) {
			cin >> a[c][d];
			if (a[c][d] == -1) {
				a[c][d] = INT_MAX / 3;
			}
		}
	}
	int ans = 0;
	priority_queue<P,vector<P>, greater<P>>Q;
	Q.push({ 0,0 });
	while (Q.size()) {
		P t = Q.top(); Q.pop();
		if (!used[t.second]) {
			ans += t.first;
			used[t.second] = true;
			for (int i = 0; i < b; i++) {
				Q.push({ a[t.second][i],i });
			}
		}
	}
	cout << ans << endl;
}

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;

int n, M[MAX][MAX];

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

int main(){
	cin >> n;
	
	for(int i=0; i < n;++i){
		for(int j=0; j < n;++j){
			int e; cin >> e;
			M[i][j] = (e == -1) ? INFTY : e;
		}
	}
	
	cout << prim() << endl;
	
	return 0;
}

C++: #include<iostream>

using namespace std;

static const int MAX = 100;
static const int NIL = (1 << 21);
static const int WHITE = 0;
static const int GREY = 1;
static const int BLACK = 2;


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

int prim() {
  int u; minv;
  int d[MAX], p[MAX], color [MAX]

  for (int i = 0; i < n; i++) {
    d[i] = INFY;
    p[i] = -1;
    color[i] = WHITE;
  }

  d[0] = 0;

  while (1) {
    minv = INFTY;
    u = -1;
    for (int i = 0; i < n; i++) {
      if (minv > d[i] && color[i] != BLACK) {
        u = i;
        minv = d[i];
      }
    }
    if (u == -1) {
      break;
    }
    color[u] = BLACK;
    for (int v = 0; i < n; i++) {
      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;
        }
      }
    }
  }
  int sum = 0;
  for (int i = 0; i < n; i++) {
    if (p[i] != -1) {
      sum += M[i][p[i]]
    }
  }

  return sum;
}

int main() {
  cin >> n;

  for (int i = 0; i < n; i++) {
    for (int j = 0; j < n; j++) {
      int e; cin >> e;
      M[i][j] = (e == -1) ? INFTY : e;
    }
  }

  cout << prim() << endl;

  return 0;
}