Go: package main

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

const (
	MAX   = 100
	INFTY = 1 << 21
	NIL   = -1
)

const (
	WHITE = iota
	GRAY
	BLACK
)

type Graph [MAX][MAX]int

func (g *Graph) prim(n int) int {
	var (
		u, minv     = 0, 0
		d, p, color [MAX]int
	)

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

	for {
		minv = INFTY
		u = -1
		for 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 v := 0; v < n; v++ {
			if color[v] != BLACK && g[u][v] != INFTY {
				if d[v] > g[u][v] {
					d[v] = g[u][v]
					p[v] = u
					color[v] = GRAY
				}
			}
		}
	}

	sum := 0
	for i := 0; i < n; i++ {
		if p[i] != -1 {
			sum += g[i][p[i]]
		}
	}

	return sum
}

func answer(reader io.Reader) string {
	sc := bufio.NewScanner(reader)
	sc.Split(bufio.ScanWords)

	sc.Scan()
	n, _ := strconv.Atoi(sc.Text())

	var g Graph
	for i := 0; i < n; i++ {
		for j := 0; j < n; j++ {
			sc.Scan()
			e, _ := strconv.Atoi(sc.Text())
			if e == -1 {
				g[i][j] = INFTY
				continue
			}
			g[i][j] = e
		}
	}

	return fmt.Sprint(g.prim(n))
}

func main() {
	fmt.Println(answer(os.Stdin))
}

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 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 <vector>
#include <algorithm>
using namespace std;
bool f[100];
int n;
int tr[100];


int trmin(){
  int res=10000,resi;
  for(int i=0;i<n;i++)
    if(f[i]==0 && tr[i]<res) res = tr[i],resi=i;
  return resi;
}


int main (){

  int mp[100][100];

  cin >> n;
  for(int i=0;i<n;i++)
    for(int j=0;j<n;j++)
      cin >> mp[i][j];

  for(int i=0;i<n;i++) f[i]=0;
  for(int i=0;i<n;i++) tr[i]=10000;
  tr[0] = 0;
  int trsum=0;

  for(int k=0;k<n;k++){
    int r=trmin();
    f[r]=1;
    trsum+=tr[r];

    for(int i=0;i<n;i++) 
      if(mp[r][i]!=-1 && f[i]==0)
	tr[i] = min(tr[i],mp[r][i]);
  }
  cout<<trsum<<endl;

  return 0;
}

C++: #include <iostream>
#define MAX 1000000000;
using namespace std;

int main(void)
{
	int n, now = 0, flag[101] = {};
	long ans = 0, an[100][100], min[100];

	cin >> n;

	for (int i = 0; i < n; i++) {
		for (int j = 0; j < n; j++)
			cin >> an[i][j];
		min[i] = MAX;
	}

	do {
		long key = MAX;
		long key_i;
		flag[now] = 1;
		flag[100] = 0;

		for (int i = 0; i < n; i++) {
			if (an[now][i] != -1 && an[now][i] < min[i] && flag[i] == 0)
				min[i] = an[now][i];
			if (flag[i] == 0 && min[i] < key) {
				key = min[i];
				key_i = i;
			}
			if (flag[i] == 1)
				flag[100]++;
		}

		now = key_i;
		ans += key;

	} while (flag[100] != n - 1);

	cout << ans << endl;

	return 0;
}

C++: #include<bits/stdc++.h>
using namespace std;
int n,a[101][101],f[101],k,edge,sum;
struct pp{
	int x;
	int y;
	int v;
}b[10001];
int getf(int u){
	if(u==f[u])return u;
	else return f[u]=getf(f[u]); 
}
int merge(int u,int v){
	int t1=getf(u);
	int t2=getf(v);
	if(t1!=t2){
		f[t2]=t1;
	} 
}
bool cmp(pp a,pp b){
	return a.v<b.v;
}
int main(){
	scanf("%d",&n);
	for(int i=0;i<n;i++)f[i]=i;
	for(int i=0;i<n;i++){
		for(int j=0;j<n;j++){
			scanf("%d",&a[i][j]);
			if(a[i][j]!=-1){
				b[k].v=a[i][j];
				b[k].x=i;b[k].y=j;
				k++;
			}
		}
	} 
	sort(b,b+k,cmp); 
//	for(int i=0;i<k;i++){
//		printf("%d %d %d\n",b[i].x,b[i].y,b[i].v);
//	}

	for(int i=0;i<k;i++){
		if(edge==n-1)break;
		if(getf(b[i].x)!=getf(b[i].y)){
			merge(b[i].x,b[i].y);
			sum+=b[i].v;edge++;
		}
	}
	printf("%d\n",sum);
	return 0;
}