Go: package main

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

const (
	WHITE int = iota
	GRAY
	BLACK
)

type graph struct {
	G [][]int
	C []int
	D []int
	P []int
}

var INFTY = 1 << 32

func constructGraph() *graph {
	sc := bufio.NewScanner(os.Stdin)
	sc.Scan()
	n, _ := strconv.Atoi(sc.Text())

	g := make([][]int, n)
	c := make([]int, n)
	d := make([]int, n)
	p := make([]int, n)

	for i := 0; i < n; i++ {
		sc.Scan()
		fields := strings.Fields(sc.Text())
		g[i] = toIntSlice(fields)
	}

	return &graph{g, c, d, p}
}

func (g *graph) initMst() {
	for i := 0; i < len(g.G); i++ {
		g.C[i] = WHITE
		g.D[i] = INFTY
	}
	g.D[0] = 0
	g.P[0] = -1
}

func (g *graph) primMst() int {
	g.initMst()

	var u int
	for {
		mincost := INFTY
		for i := 0; i < len(g.G); i++ {
			if g.C[i] != BLACK && g.D[i] < mincost {
				mincost = g.D[i]
				u = i
			}
		}

		if mincost == INFTY {
			break
		}

		g.C[u] = BLACK

		for i := 0; i < len(g.G); i++ {
			if g.C[i] != BLACK && g.existEdge(u, i) {
				if g.G[u][i] < g.D[i] {
					g.D[i] = g.G[u][i]
					g.P[i] = u
				}
			}
		}
	}

	totalCost := 0
	for _, cost := range g.D {
		totalCost += cost
	}
	return totalCost
}

func (g *graph) existEdge(u, v int) bool {
	return g.G[u][v] != INFTY && g.G[v][u] != INFTY
}

func toIntSlice(s []string) []int {
	a := make([]int, len(s))
	for i, v := range s {
		num, _ := strconv.Atoi(v)
		if num == -1 {
			num = INFTY
		}
		a[i] = num
	}
	return a
}

func main() {
	g := constructGraph()
	fmt.Println(g.primMst())
}

C++: #include <iostream>
using namespace std;
static const int MAX = 10;
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>
#include<cstring>
#include<algorithm>
using namespace std;

#define WHITE 0
#define GRAY 1
#define BLACK 2
#define INF 2000000000

int x[10000][10000];
int color[10000];
int MIN[10000];
int sum;
int sum_min = INF;

int main() {
	int n, a, b, c;
	cin >> n;
	for (int i = 0; i < n; i++) {
		for (int j = 0; j < n; j++) {
			cin >> x[a][b];
		}
	}
	for (int i = 0; i < n; i++) {
		memset(MIN, 0, sizeof(MIN));
		b = INF;
		a = 1;
		color[i] = GRAY;
		MIN[i] = 0;
		while (a >= 1) {
			for (int j = 0; j < n; j++) {
				if (color[j] = GRAY) {
					if (b > MIN[j]) {
						b = MIN[j];
						c = j;
					}
				}
			}
			color[c] = BLACK;
			a -= 1;
			for (int j = 0; j < n; j++) {
				if (color[j] != BLACK && x[c][j] != -1) {
					if (color[i] == WHITE) {
						a += 1;
					}
					color[j] = GRAY;
					MIN[j] = min(x[c][j], MIN[j]);
				}
			}
		}
		sum = 0;
		for (int j = 0; j < n; j++) {
			sum += MIN[j];
		}
		sum_min = min(sum_min, sum);
	}
	cout << sum_min << endl;
	return 0;
}

C++: #include <bits/stdc++.h>
#define rep(i,n) for(int i=0;i<(int)(n);i++)
using namespace std;
using ll = long long ;
using P = pair<int,int> ;
using pll = pair<long long,long long>;
constexpr int INF = 1e9;
constexpr long long LINF = 1e17;
constexpr int MOD = 1000000007;
constexpr double PI = 3.14159265358979323846;


struct Unionfind{
    vector<int> parents;
    int n;
    Unionfind(int n):n(n),parents(n,-1){ }

    int find(int x){
        if(parents[x] < 0) return x;
        else return parents[x] = find(parents[x]);
    }

    void unite(int x,int y){
        x = find(x);
        y = find(y);

        if(x==y) return;
        if(parents[x] > parents[y]) swap(x,y);
        parents[x] += parents[y];
        parents[y] = x;
    }  

   int size(int x){
       return -parents[find(x)];
   }

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

   vector<int> members(int x){
       int root = find(x);
       vector<int> member;
       for(int i=0;i<n;i++){
           if(find(i)==root){
               member.push_back(i);
           }
       }
      return member;
  }

  int group_cnt(){
      int c = 0;
      rep(i,n){
          if(parents[i] < 0) ++c;
      }
      return c;
  }
};

struct edge{
    int from,to,cost;  
};

int main(){
    int n;
    cin >> n;
    vector<edge> eg;
    rep(i,n)rep(j,n){
        int a;
        cin >> a;
        if(i > j) continue;
        if(a==-1) continue;
        eg.push_back(edge{i,j,a});
    }

    sort(eg.begin(),eg.end(),[](const edge &l,const edge &r){
        return l.cost < r.cost;
    });

    Unionfind uf(n);
    int ans = 0;

    rep(i,eg.size()){
        if(uf.same(eg[i].from,eg[i].to)) continue;
        uf.unite(eg[i].from,eg[i].to);
        ans += eg[i].cost;
    }
    
    cout << ans << endl;
    return 0;
}

C++: #include <bits/stdc++.h>
using namespace std;

#define INF 1000000
#define N_MAX 100
#define WH 0
#define GR 1
#define BK 2

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

    int color[N_MAX] = {};
    int d[N_MAX];
    for (int i = 0; i < n; i++) {
        d[i] = INF;
    }
    int p[N_MAX] = {};

    while (true) {
        int u;
        int min_cost = INF;
        d[0] = 0;
        p[0] = -1;

        for (int i = 0; i < n; i++) {
            if (color[i] != BK && d[i] < min_cost) {
                min_cost = d[i];
                u = i;
            }
        }
        if (min_cost == INF) {
            break;
        }
        color[u] = BK;

        for (int v = 0; v < n; v++) {
            if (color[v] != BK && A[u][v] != INF) {
                if (A[u][v] < d[v]) {
                    d[v] = A[u][v];
                    p[v] = u;
                    color[v] = GR;
                }
            }
        }
    }

    int ans = 0;
    for (int i = 0; i < n; i++) {
        ans += d[i];
    }
    cout << ans << endl;

    return 0;
}

C++: #include <cstdio>
#include <iostream>
#include <queue>
#include <utility>

using namespace std;

const int NIL = 2001;
const int MAX = 100;
int G[MAX][MAX];
int W[MAX];
int n;

void MST() {
	priority_queue<pair<int, int>> PQ;
	PQ.push(make_pair(0, 0));
	W[0] = 0;
	while (!PQ.empty()) {
		int u = PQ.top().second;
		PQ.pop();
		for (int i = 0; i < n; ++i) {
			if (G[u][i] != -1 && G[u][i] < W[i]) {
				PQ.push(make_pair(G[u][i] * -1, i));
				W[i] = G[u][i];
			}
		}
	}
}

int main() {

	scanf("%d", &n);
	for (int i = 0; i < n; ++i) {
		for (int j = 0; j < n; ++j)
			G[i][j] = NIL;
		W[i] = NIL;
	}

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

	MST();

	int sum = 0;
	for (int i = 0; i < n; ++i) {
		sum += W[i];
	}
	cout << sum << endl;

	return 0;
}