Go: package main

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

type color int

const (
	white color = iota // 未訪問
	mst                // MSTとして確定
)

// 頂点
type node struct {
	matrix   []int // 隣接行列
	minToMst int   // MSTへの重み最小値
	parent   int   // 最小値の相手
	color    color
}

func main() {
	scanner := bufio.NewScanner(os.Stdin)
	n := eGetInt(scanner)

	nodes := make([]node, n)
	for i := 0; i < n; i++ {
		nodes[i].matrix = eAtoi((strings.Fields(eGetline(scanner))))
		nodes[i].parent = -1
		nodes[i].minToMst = math.MaxInt16
		nodes[i].color = white
	}

	// 初回はnode[0]がMSTに入るように,minToMstを設定
	nodes[0].minToMst = 0
	for { // 全部チェックするまで

		// どの頂点を新たにMSTに取り込むか
		min := math.MaxInt16
		u := -1
		for i := 0; i < n; i++ {
			if nodes[i].color == mst {
				continue
			}
			if nodes[i].minToMst < min {
				u = i
				min = nodes[i].minToMst
			}
		}

		if u == -1 {
			break
		}
		// MSTに追加する頂点決定
		nodes[u].color = mst

		// MSTに属していない頂点それぞれについて,MSTとの最小の重みを更新
		for i := 0; i < n; i++ {
			if nodes[i].color == mst {
				continue
			}
			if nodes[i].matrix[u] == -1 {
				// 接してない
				continue
			}
			if nodes[i].matrix[u] < nodes[i].minToMst {
				// node[u]との重みが最小
				nodes[i].minToMst = nodes[i].matrix[u]
				nodes[i].parent = u
			}
		}
	}

	sum := 0
	for _, v := range nodes {
		// node[0]はparentが入っていない
		if v.parent != -1 {
			sum += v.matrix[v.parent]
		}
	}
	fmt.Println(sum)
}

func eGetInt(scanner *bufio.Scanner) int {
	t := eAtoi(strings.Fields(eGetline(scanner)))
	return t[0]
}

func eGetline(p *bufio.Scanner) string {
	if !p.Scan() {
		if err := p.Err(); err != nil {
			log.Fatal(err.Error())
		}
		return ""
	}
	return p.Text()
}

func eAtoi(s []string) []int {
	ints := make([]int, len(s))
	var err error
	for i, e := range s {
		ints[i], err = strconv.Atoi(e)
		if err != nil {
			log.Fatal(err.Error())
		}
	}
	return ints
}

C++: #include<iostream>
#include<cstdio>
#include<vector>
#include<queue>
#include<map>
#include<string>
#include<algorithm>
#include<functional>
#define ll long long
#define inf  999999999
#define pa pair<int,int>

using namespace std;

int n,a[200][200]={0};
void prim(){
	int d[200]={0};
	priority_queue<pair<int,pa> >  PQ; 
	pair<int,pa> q;
	pa r;
	int wei=0;
	int w=6;
	int u=w,z=0;
	d[w]=1;
	while(z!=n-1){
		for(int j=0;j<n;j++){
			if(a[u][j]<0 && d[j]==0 && u!=j) PQ.push(make_pair(a[u][j],make_pair(u,j)));
		}
	while(1){
		if(PQ.size()==0) {
			cout<<"dv"<<endl;
		break;
		}
		q=PQ.top();
		PQ.pop();
		r=q.second;
	//	cout<<"rsec"<<r.second<<endl;
		if(d[r.second]==0) break;
		
		}
	u=r.second;
//	cout<<"a" <<u<<endl;
	d[u]=1;
	wei=wei+q.first;
	z++;
//	cout<<z<<" "<<-q.first<<" "<<u<<" "<<r.first<<endl;
	
	}
	cout<<-wei<<endl;
}



int main(){
	// your code goes here
	int m;
	cin>>n;
	
	for(int i=0;i<n;i++){
		for(int j=0;j<n;j++){
		cin>>m;
		a[i][j]=-m;
		}
	}
	prim();

	return 0;
}

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

static const int N = 100;
static const int INF = (1 << 30);
static const int WHITE = 0;
static const int GRAY = 1;
static const int BLACK = 2;


int n;
int m[N][N];

int prim(){
    int u,min_val;
    int d[N],p[N],color[N];

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

    d[0] = 0;
    while(1){
        min_val = INF;
        u = -1;
        for(int i=0;i<n;i++){
            if(min_val > d[i] && color[i] != BLACK){
                u = i;
                min_val = 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;
}


//mainは問題なし
int main(){
    int in_val;
    cin >> n;
    for(int i=0;i<n;i++){
        for(int j=0;j<n;j++){
            cin >> in_val;
            if(in_val == -1)
                in_val = INF;
            m[i][j] = in_val;
        }
    }

    cout << prim() << endl;

}

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

const static int MAX = 100;
const static int INFTY = (1<<21);
const static int WHITE = 0;
const static int GRAY = 1;
const static 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(true){
    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 work;
      cin >> work;
      M[i][j] = (work == -1) ? INFTY : work;
    }
  }

  cout << prim() << endl;


  return 0;
}

C++: #include <iostream>
#include <queue>
#define INF 200000
using namespace std;
typedef pair<int,int> P;
P a;
priority_queue< P,vector<P> ,greater<P> > pq;
int map[101][101];
bool decided[101];
int sum,n;
int node,count;
void check(){
	node=1;
	decided[node]=true;
	count=n-1;
	while(1){
		for(int i=1;i<=n;i++){
			if(map[node][i]!=-1&&!decided[i]){
				a=make_pair(map[node][i],i);
				pq.push(a);
			}
		}
		while(decided[pq.top().second])pq.pop();
		sum+=pq.top().first;
		node=pq.top().second;
		decided[node]=true;
		count--;
		if(count==0)break;
		pq.pop();
	}
}

int main(){
	cin >>n;
	for(int i=1;i<=n;i++){
		for(int j=1;j<=n;j++){
			cin >> map[i][j];
		}
	}
	sum=0;
	check();
	cout << sum<<endl;
}