Go: package main

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

//util
var sc = bufio.NewScanner(os.Stdin)

func nextStr() string {
	sc.Scan()
	return sc.Text()
}

func nextInt() int {
	sc.Scan()
	i, e := strconv.Atoi(sc.Text())
	if e != nil {
		panic(e)
	}
	return i
}

func printList(list []int) {
	n := len(list)
	buf := bufio.NewWriter(os.Stdout)
	for _, v := range list[0 : n-1] {
		buf.Write([]byte(fmt.Sprintf("%d ", v)))
	}
	buf.Write([]byte(fmt.Sprintf("%d\n", list[n-1])))
	buf.Flush()
}

func max(a, b int) int {
	if a > b {
		return a
	} else {
		return b
	}
}

func min(a, b int) int {
	if a > b {
		return b
	} else {
		return a
	}
}

//solve
const (
	MAX   = 100
	INFTY = (1 << 21)
	WHITE = 0
	GRAY  = 1
	BLACK = 2
)

//V: グラフの頂点全体の集合
//T: MSTに属する頂点の集合
var (
	n     int
	M     [MAX][MAX]int //重みを記録する隣接行列
	color [MAX]int
	p     [MAX]int //MSTにおける頂点の親を記録
	d     [MAX]int //Tに属する頂点と、V−Tに属する頂点を繋ぐ辺の中で、重みが最小のものを記録
)

func prim() int {
	var u, minv int
	//初期化
	for i := 0; i < n; i++ {
		d[i] = INFTY
		p[i] = -1
		color[i] = WHITE
	}

	d[0] = 0

	for {
		//頂点uを決めていく
		//つまり、Tに属する頂点と、V−Tに属する頂点を繋ぐ辺の中で、重みが最小のものを決める
		minv = INFTY
		u = -1
		for i := 0; i < n; i++ {
			//未訪問かつ、辺の重みが最小となるuを選ぶ
			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++ {
			//未訪問かつ、辺が存在するとき
			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
				}
			}
		}
	}

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

func main() {
	sc.Split(bufio.ScanWords)
	n = nextInt()

	for i := 0; i < n; i++ {

		for j := 0; j < n; j++ {
			tmp := nextInt()
			if tmp == -1 {
				tmp = INFTY
			}
			M[i][j] = tmp
		}

	}

	fmt.Println(prim())

}

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

int x[10000][10000];
int MIN[10000];
int MINX = 0;
int MINZ = 100;

int main() {
	memset(MIN, 127, sizeof(MIN));
	int n, a;
	cin >> n;
	for (int i = 0; i < n; i++) {
		for (int j = 0; j < n; j++) {
			cin >> a;
			x[i][j] = a;
		}
	}
	for(int h=0;h<n;h++){
		memset(MIN, 127, sizeof(MIN));
		MINX=0;
		MIN[h] = 0;
		for (int i = 0; i < n; i++) {
			for (int j = 0; j < n; j++) {
				for (int k = 0; k < n; k++) {
					if (x[j][k] != -1) {
						MIN[k] = min(MIN[k], x[j][k]);
					}
				}
			}
		}
		for (int i = 0; i < n; i++) {
			MINX += MIN[i];
		}
		MINZ=min(MINZ,MINX);
	}
	cout << MINZ << endl;
	return 0;
}

C++: #include<stdio.h>
#include<queue>
#include<vector>
using namespace std;
const int maxn = 1010;
const int INFTY = 1000000000;
struct Node{
    int to;
    int value;
    void set(int a,int b){
        to  = a;
        value = b;
    }
    void real(){
        value*=-1;
    }
};
bool operator<(const Node&a,const Node &b){
    return a.value<b.value;
}
vector<Node> g[maxn];
priority_queue<Node> q;
int d[maxn];
bool vis[maxn];
int p[maxn];
int n;
void prim(){
    for(int i = 0;i<n;++i){
        d[i] = INFTY;
        vis[i] = false;
        p[i] = -1;
    }
    d[0] = 0;
    Node work;
    work.set(0,0);
    q.push(work);
    while(!q.empty()){
        work = q.top();
        work.real();
        q.pop();
        int from = work.to;
        int len = g[from].size();
        if(vis[from])continue;
        vis[from] = true;
        while(len--){
            int to = g[from][len].to;
            int add = g[from][len].value;
            if(!vis[to]&&(add<d[to])){
                d[to] = add;
                p[to] = from;
                work.set(to,d[to]);
                work.real();
                q.push(work);
            }
        }
    }
}
int main(){
    int tmp,ans;
    Node work;
    scanf("%d",&n);
    for(int i = 0;i<n;++i){
        for(int j  = 0;j<n;++j){
            scanf("%d",&tmp);
            if(tmp!=-1){
                work.set(j,tmp);
                g[i].push_back(work);
            }
        }
    }
    prim();
    ans = 0;
    for(int i = 0;i<n;++i){
        ans+=d[i];
    }
    printf("%d\n",ans);
    return 0;
}

C++: #include<iostream>
#include<algorithm>

using namespace std;

#define INF 2001
#define NIL -2


struct node{
    int key=INF, pi=NIL, flag=0;
};

node grf[101];
int hv[101][101], n;

void search(){
    int min = INF, mini = NIL;
    for(int i=0;i<n;++i){
        if(grf[i].flag != 1 && grf[i].key < min){
            min = grf[i].key;
            mini= i;
        }
    }
    
    if(min == INF){
        return;
    }
    
    grf[mini].flag = 1;
    for(int j=0;j<n;++j){
        if((grf[j].flag != 1 && hv[mini][j] != -1) && hv[mini][j] < grf[j].key){
            grf[j].key = hv[mini][j];
            grf[j].pi = mini;
        }
    }
    
    return;
    
}

int main(){
    int total=0;
    cin >> n;
    for(int i=0;i<n;++i){
        for(int j=0;j<n;++j){
            cin >> hv[i][j];
        }
    }
    
    grf[0].key = 0;
    grf[0].flag = 1;
    for(int j=0;j<n;++j){
        if(hv[0][j] != -1 && hv[0][j] < grf[j].key){
            grf[j].key = hv[0][j];
            grf[j].pi = 0;
        }
    }
    
    for(int i=1;i<n;++i){
        search();
    }
    
    for(int i=0;i<n;++i){
        total+=grf[i].key;
    }
    
    cout << total << endl;
    
    return 0;
}

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

int a[100][100];
bool r[100];


int main()
{
    ios::sync_with_stdio(false);
    cin.tie(0);
    int n;
    cin>>n;
    for(int i=0; i<n; i++) {
        for(int j=0; j<n; j++) {
            cin>>a[i][j];
        }
    }
    priority_queue<pair<int,int>, vector<pair<int,int> >, greater<pair<int,int> > >q;
    q.push(make_pair(0,0));
    int cost=0;
    pair<int,int> e;
    while(!q.empty()) {
        e=q.top();
        q.pop();
        if(r[e.second]) continue;
        r[e.second]=true;
        cost+=e.first;
        for(int i=0; i<n; i++) {
            if(a[e.second][i]!=-1) q.push(make_pair(a[e.second][i], i));
        }
    }
    cout<<cost<<'\n';
    return 0;
}

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

using namespace std;

#define N 101

int main(){

  int n;

  int g[N][N];
  int min=3000;
  int weight[N];
  int sum=0;

  //load n
  cin >>n;

  //load data
  for(int i=1;i<=n;i++){
    weight[i]=0;
    for(int j=1;j<=n;j++){
      scanf("%d",&g[i][j]);
    }
  }

  for(int i=1;i<=n;i++){
    for(int j=1;j<=n;j++){
      if(g[i][j]!= -1 && g[i][j]<min) {
	min=g[i][j];
      }
	weight[i]=min;
    }
  }

  for(int i=1;i<=n;i++){
    if(weight[i]!=3000) sum+=weight[i];
  }
  //print
  cout <<sum<<endl;

  return 0;

}

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

#define N 120
int n;

int g[N][N];
int mini;
int weight[N];
bool us[N];

int prim(){
  int v;
  int ans=0;
  weight[1]=0;
  
  while(true){
    v=-1;
   
    for(int i=1;i<=n;i++){
      if(us[i]!=true && (v==-1 ||weight[i]<weight[v]))v=i;
    }

    if(v==-1)break;
    us[v]=true;
    ans+=weight[v];

    for(int i=1;i<=n;i++){
      if(weight[i]>g[v][i])weight[i]=g[v][i];
      else weight[i]=weight[i];
    }
  }
  return ans;
}


int main(){

  //load n
  cin >>n;

  //load data
  for(int i=1;i<=n;i++){
    weight[i]=INT_MAX;
    us[i]=false;
    for(int j=1;j<=n;j++){
      scanf("%d",&g[i][j]);
      if(g[i][j]== -1)g[i][j]=INT_MAX;
      //    cout <<g[i][j]<<" ";
    }
    //    cout <<endl;
  }




  //print
  cout <<prim()<<endl;

  return 0;

}