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>
#include<vector>
#include<algorithm>
using namespace std;

typedef int Weight;
struct Edge{
	int src,dst;
	Weight weight;
};

bool asc(const Edge &e,const Edge &f){
	return e.weight < f.weight;
}

vector<Edge> Edges;
vector<int> L(100005,-1);

int check(Edge &e,int n){
	int j;
	if (L[e.src]!=L[e.dst]){
		int t = L[e.dst];
		for (j=0;j<n;j++){
			if (L[j]==t){
				L[j]=L[e.src];
			}
		}
		return 1;
	}else{
		return 0;
	}
}

int main(){
	int n,m,i,j,w;
	cin >> n ;
	
	for (i=0;i<n;i++){
		for(j=0;j<n;j++){
			cin >> w;
			if ((w!=-1)&&(i>j)){
				Edge edge={i,j,w};
				Edges.push_back(edge);
			}
		}
	}
	
	sort(Edges.begin(),Edges.end(),asc);
	
	m = Edges.size();
	
	for (j=0;j<n;j++){
		L[j]=j;
	}
	
	int TotalWeight=0;
	int count=0;
	int k;
	for (i=0;i<m;i++){
		if (count==n-1){break;}
		if (check(Edges[i],n)){
			TotalWeight+=Edges[i].weight;
			count++;
		}
	}
	cout << TotalWeight<<endl;
	return 0;
}

C++: #include <stdio.h>

const int WHITE = 0;
const int GRAY = 1;
const int BLACK = 2;
const int N = 100;
const int INF = 2000000000;

int g[N + 1][N + 1];
int d[N + 1], p[N + 1], color[N + 1];
int n;

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

	while (true)
	{
		int min = INF;
		int u = -1;
		for (int i = 1; i <= n; i++)
		{
			if (color[i] != BLACK && d[i] < min)
			{
				min = d[i];
				u = i;
			}
		}
		if (u == -1)
			break;

		color[u] = BLACK;

		for (int i = 1; i <= n; i++)
		{
			if (color[i] != BLACK && g[u][i] != INF && d[i] > g[u][i])
			{
				d[i] = g[u][i];
				color[i] = GRAY;
				p[i] = u;
			}
		}
	}
	int sum = 0;
	for (int i = 1; i <= n; i++)
	{
		if (p[i] != -1)
			sum += g[p[i]][i];
	}
	printf("%d\n", sum);
}

int main()
{
	scanf("%d", &n);
	for (int i = 1; i <= n; i++)
		for (int j = 1; j <= n; j++)
		{
			scanf("%d", &g[i][j]);
			if (g[i][j] == -1)
				g[i][j] = INF;
		}
	prim();

	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]];
  }
  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 "stdio.h"

#define MAX 100
#define INFTY 1<<21
#define WHITE 0
#define GRAY 1
#define BLACK 2

int n, M[MAX][MAX];

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

  for(i=0; i<n; i++){
    d[i] = INFTY;
    p[i] = -1;
    color[i] = WHITE;
  }
  d[0] = 0;
  while (1) {
    minv = INFTY;
    u = -1;
    for(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(i=0; i<n; i++)
  if(p[i]!=-1) sum += M[i][p[i]];

  return sum;
}

int main(){
  int i, j, e;
  scanf("%d", &n);
  for(i=0; i<n; i++){
    for(j=0; j<n; j++){
      scanf("%d", &e);
      if(e == -1){
        M[i][j] = INFTY;
      }else{
        M[i][j] = e;
      }
    }
  }
  printf("%d\n", prim());

  return 0;

}

C++: #include<iostream>
using namespace std;
static const int M = 100;
static const int INF = (1<<21);
static const int W = 0;
static const int G = 1;
static const int B = 2;

int n, m[M][M];

int prim() {
	int u, minv,sum=0;
	int i,v,d[M], p[M], c[M];

	for (i = 0; i < n; i++) {
		d[i] = INF;
		p[i] = -1;
		c[i] = W;
	}
	d[0] = 0;
	while (1) {
		minv = INF;
		u = -1;
		for (i = 0; i < n; i++) {
			if (minv > d[i] && c[i] != B) {
				u = i;
				minv = d[i];
			}
		}
		if (u == -1) {
			break;
		}
		c[u] = B;
		for (v = 0; v < n; v++) {
			if (c[v] != B && m[u][v] != INF) {
				if (d[v] > m[u][v]) {
					d[v] = m[u][v];
					p[v] = u;
					c[v] = G;
				}
			}
		}
	}
	for (i = 0; i < n; i++) {
		if (p[i] != -1) {
			sum += m[i][p[i]];
		}
	}
	return sum;
}

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

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

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

int parent[100],height[100];

bool comp(const edge& e1,const edge& e2){
	return e1.cost < e2.cost;
}

int find(int x){
	if(parent[x] == x) return x;
	else return parent[x] = find(parent[x]);
}

void unite(int x,int y){
	x = find(x);
	y = find(y);
	if(x == y) return;
	if(height[x] < height[y]){
		parent[x] = y;
	}else {
		parent[y] = x;
		if(height[x] == height[y]) height[x]++;
	}
}

bool same(int x,int y){
	return find(x) == find(y);
}

int main(){
	int n,res = 0;
	cin >> n;
	vector<edge> es;
	for(int i = 0;i < n;i++) parent[i] = i;
	for(int i = 0;i < n;i++){
		for(int j = 0;j < n;j++){
			int t;
			cin >> t;
			if(t != -1) es.push_back({i,j,t});
		}
	}
	sort(es.begin(),es.end(),comp);
	for(int i = 0;i < es.size();i++){
		edge e = es[i];
		if(!same(e.a,e.b)){
			unite(e.a,e.b);
			res += e.cost;
		}
	}
	cout << res;
	return 0;
}

C++: #include <utility>
#include <string>
#include <vector>
#include <algorithm>
#include <iostream>
using namespace std;

int n;
int a[100][100] = {0};
int f[100] = {0};
int c = -1;

int kansu( int i, int t, int s ){
	f[i] = s;
	t++;
	if ( t != n ) {
		for ( int j = 0; j < n; j++ ) {
			if ( a[i][j] != -1 && f[j] == -1 ) kansu( j, t, s + a[i][j] );
		}
	}else {
		if ( c == -1 || c > s ) c = s;
	}
	f[i] = -1;
	return 0;
}

int main(){
	cin >> n;
	int s;
	for ( int i = 0; i < n; i++ ) {
		for ( int j = 0; j < n; j++ ) {
			cin >> a[i][j];
		}
		f[i] = -1;
	}
	for ( int i = 0; i < n; i++ ) {
		kansu(i,0,0);
	}
	cout << c << endl;
	return 0;
}