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 <vector>

using namespace std;
const int INF = 1001001001;

int prim(vector< vector<int> > cost)
{
    vector<int> V(1, 0), T(cost.size());
    for(int i=0;i<cost.size();++i) T[i] = i;
    T[0] = INF;
    int mini, minj, min_cost, ans=0;
    while(V.size() < cost.size())
    {
        min_cost = INF;
        for(int i : V){
            for(int j : T)
            {
                if(j == INF) continue;
                if(cost[i][j] < min_cost)
                {
                    mini = i;
                    minj = j;
                    min_cost = cost[i][j];
                }
            }
        }
        V.push_back(minj);
        T[minj] = INF;
        cost[mini][minj] = cost[minj][mini] = INF;
        ans += min_cost;
    }
    return ans;
}

int main()
{
    int n;
    cin >> n;
    vector<vector<int> > cost(n, vector<int>(n));

    for(int i=0;i<n;++i)
    {
        for(int j=0;j<n;++j)
        {
            cin >> cost[i][j];
            if(cost[i][j] == -1) cost[i][j] = INF;
        }
    }

    cout << prim(cost) << endl;
}

C++: #include <stdio.h>

int n,M[110][110];

int minimum(){
  int color[110],d[110],p[110];
  int i=0,s=0;
  int mincost,v,u;
  while(i<=n){color[i]=0;d[i]=5000;p[i]=-1;i++;}
  d[0]=0;
  while(1){
    mincost = 5000;
    for(i=0;i<n;i++){
      if(color[i] != 2 && d[i]<mincost){
	mincost = d[i];
	u=i;
      }
    }
    if(mincost == 5000){
      break;
    }
    color[u] = 2;
    for(v=0;v<n;v++){
      if(color[v] != 2 && M[u][v]<d[v] && M[u][v]!=-1){
	d[v] = M[u][v];
	p[v] = u;
	color[v] = 1;
      }
    }
  }
  for(i=0;i<n;i++){
    if(d[i]!=5000) s+=d[i];
  }
  return s;
}
int main(void){
  int i,j;
  scanf("%d",&n);
  for(i=0;i<n;i++){
    for(j=0;j<n;j++){
      scanf("%d",&M[i][j]);
    }
  }
  printf("%d\n",minimum());
  return 0;
}

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

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

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));
		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 <iostream>
#include <iomanip>
#include <vector>
#include <stack>
#include <queue>
#include <set>
#include <map>
#include <algorithm>
#include <cstdio>
#include <utility>
#include <string>
#include <cmath>
#include <cstdlib>
#include <cstring>

using namespace std;

typedef uint64_t u64;
typedef int64_t s64;
typedef uint32_t u32;
typedef int32_t s32;
typedef vector<s32> vs32;
typedef vector<u32> vu32;
typedef vector<s64> vs64;
typedef vector<u64> vu64;

const double PI=3.14159265358979323846;

#define MAX(x, y) ((x) < (y) ? (y) : (x))
#define MIN(x, y) ((x) > (y) ? (y) : (x))

#define rep(i, N) for(int i = 0; i < N; ++i)

#define CEIL(x, y) (((x) + (y) - 1) / (y))
#define MOD 1000000007ULL

int main()
{
    cin.tie(0);
    ios::sync_with_stdio(false);

    int n;
    cin >> n;

    int g[n][n];
    int w;
    rep (i, n)
    {
        rep (j, n)
        {
            cin >> w;
            if (w < 0) w = 1e9;
            g[i][j] = w;
        }
    }

    u64 ans = 0;
    vs32 MST;
    vs32 remain(n - 1);
    rep (i, n - 1) remain[i] = i + 1;
    MST.push_back(0);
    while (MST.size() < n)
    {
        w = 1e9;
        int node;
        for (int u : MST)
        {
            rep (j, remain.size())
            {
                int v = remain[j];
                if (w > g[u][v])
                {
                    w = g[u][v];
                    node = j;
                }
            }
        }
        MST.push_back(remain[node]);
        swap(remain[node], remain.back());
        remain.pop_back();
        ans += w;
    }

    cout << ans << "\n";
    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;
}