Go: package main

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

const BIG_COST = 3000

const (
	ST_NOT_YET = iota
	ST_JOINED
)

func main() {
	sc := bufio.NewScanner(os.Stdin)
	sc.Split(bufio.ScanWords)

	nNodes := scanInt(sc)
	costs := make([][]int, nNodes)

	for r := 0; r < nNodes; r++ {
		costs[r] = make([]int, nNodes)
		for c := 0; c < nNodes; c++ {
			costs[r][c] = scanInt(sc)
		}
	}

	states := make([]int, nNodes)
	minCosts := make([]int, nNodes)

	for i := 1; i < nNodes; i++ {
		minCosts[i] = BIG_COST
	}

	for {
		var u int
		minCost := BIG_COST

		for i := 0; i < nNodes; i++ {
			if states[i] != ST_JOINED && minCosts[i] < minCost {
				minCost = minCosts[i]
				u = i
			}
		}

		// 全てのノードが MST に JOIN できたので終了。
		if minCost == BIG_COST {
			break
		}

		states[u] = ST_JOINED

		for v := 0; v < nNodes; v++ {
			cost := costs[u][v]

			// MST内の u と MST外の v との辺の重みをそれぞれ minCosts[v] として
			// 保存しておく。このうち辺の重みが最小となる v が次のループで MST に JOIN する。
			if states[v] != ST_JOINED && cost != -1 && cost < minCosts[v] {
				minCosts[v] = cost
			}
		}
	}

	sum := 0
	for _, cost := range minCosts {
		sum += cost
	}
	fmt.Println(sum)
}

func scanInt(sc *bufio.Scanner) int {
	sc.Scan()
	v, _ := strconv.Atoi(sc.Text())
	return v
}

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

int x[10000][10000];
int MIN[10000];
int MINX = 0;
int MINZ = 10000000;

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 i=0;i<n;i++){
	    for(int j=0;j<n;j++){
	        if(x[i][j]!=-1){
	            MIN[i]=min(x[i][j],MIN[i]);
	        }
	    }
	}
	for(int i=0;i<n;i++){
	    MINX=0;
	    for(int j=0;j<n;j++){
	        MINX += MIN[j];
	    }
	    MINX -= MIN[i];
	    MINZ=min(MINZ,MINX);
	}
	cout<<MINZ<<endl;
	return 0;
}

C++: #define  _CRT_SECURE_NO_WARNINGS
#include <iostream>
#include <stdio.h>
#define INF 20000202
#define maxn 101
using namespace std;

int M[maxn][maxn] = {}, d[maxn] = {}, p[maxn] = {}, s[maxn] = {};
int n;

void Prim()
{
	for (int i = 0; i < n; i++)
		d[i] = INF;
	d[0] = 0;
	p[0] = -1;
	while (true)
	{
		int u = -1, mincost = INF;
		for(int i=0;i<n;i++)
			if (s[i] == 0 && d[i] < mincost)
			{
				mincost = d[i];
				s[i] = 1;
				u = i;
			}
		if (u == -1)break;
		for(int v=0;v<n;v++)
			if (M[u][v] != -1 && M[u][v] < d[v] && s[v] == 0)
			{
				d[v] = M[u][v];
				p[v] = u;
			}
	}
}

int main()
{
	int sum = 0;
	scanf("%d", &n);
	for (int i = 0; i < n; i++)
		for (int j = 0; j < n; j++)
			scanf("%d", &M[i][j]);
	Prim();
	for (int i = 0; i < n; i++)
	{
		sum += d[i];
	}
	printf("%d", sum);
	return 0;
}

C++: #include<iostream>
#include<algorithm>
#define INF 99999
using namespace std;

int G[110][110] = {};

int prim(int n)
{
    int mini[110];
    int used[110];

    //init
    for(int i = 0;i < n;i++){
        mini[i] = INF;
        used[i] = 0;
    }
    mini[0] = 0;
    int ans = 0;

    while(true)
    {
        int v = -1;
        for(int i = 0;i < n;i++){
            if(!used[i] && (v == -1 || mini[i] < mini[v])) v = i;
        }
        if(v == -1) break;
        //ans = -1;

        used[v] = 1;
        ans += mini[v];
        //cout << ans << endl;

        for(int i = 0;i < n;i++){
            mini[i] = min(mini[i], G[v][i]);
        }
    }
    return ans;
}

int main()
{
    int n;
    cin >> n;

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

    cout << prim(n) << endl;
    return 0;
}

C++: #include "bits/stdc++.h"
using namespace std;
typedef long long ll;
typedef vector<vector<int> > vvi;
typedef vector<int> vi;
typedef vector<string> vs;
typedef pair<string, int> psi;
typedef pair<int, int> pii;
#define rep(i,s,n) for(int i = (s); i < (n); i++)
#define loop(i) for(int i = 0;true; i++)
#define all(x) (x).begin(), (x).end()
#define yn(f) (f?"yes":"no")
#define YN(f) (f?"YES":"NO")
#define Yn(f) (f?"Yes":"No")
#define mn 1000000007
#define INT32_MAX 2147483647

int main() {
	int N;
	cin >> N;
	vvi A(N,vi(N));
	for (int i = 0; i < N; i++)
	{
		for (int j = 0; j < N; j++)
		{
			cin >> A[i][j];
			if (A[i][j] == -1)A[i][j] = INT32_MAX;
		}
	}
	vi used(N, 0);
	vi mincost(N,INT32_MAX);
	int total = 0;
	mincost[0] = 0;
	while (true) {
		int minIndex = -1;
		for (int u = 0; u < N; u++) {
			if (used[u]==0 && (minIndex == -1 || mincost[u] < mincost[minIndex])) minIndex = u;
		}
		if (minIndex == -1) break;
		used[minIndex] = 1;
		total += mincost[minIndex];
		for (int u = 0; u < N; u++)
		{
			mincost[u] = min(mincost[u], A[minIndex][u]);
		}
	}
	cout << total << endl;
};

C++: #include <iostream>
using namespace std;
 
int n;
int a[101][101];
int flg[101];
int t[101];
int sum = 0;
 
void visit(){
  int ima = 0;
  int mine = 100000000;
   
   
  for(int k=0;k<n-1;k++) {
    mine = 10000000;
    for(int i=0;i<n;i++) {
      if(flg[i] == 0 && mine > t[i]) {
    mine = t[i];
    ima = i;
      }
    }
    sum += mine;
    flg[ima] = 1;
     
    for(int i=0;i<n;i++) 
      if(a[ima][i] != -1) 
    if(t[i] > a[ima][i] ) t[i] = a[ima][i];
     
     
  }
}
 
int main() {
 
  cin >> n;
 
  for(int i=0;i<n;i++) 
    for(int j=0;j<n;j++) 
      cin >> a[i][j];
   
  for(int i=0;i<n;i++) {
    flg[i] = 0;
    t[i] = 100000000;
  }
   
  t[0] = 0;
  flg[0] = 1;
  for(int i=0;i<n;i++) 
    if(a[0][i] != -1) t[i] = a[0][i];
 
  visit();
 
  cout << sum << endl;
  
  return 0; 
   
}

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

int prim();
int Infty = 20000000;

int n,*d,*p,**G;
string *color;

int main(){
	cin>>n;
	d = new int[n]; p = new int[n];
	d = d-1; p = p-1;
	G = new int*[n]; for(int i=0;i<n;i++) G[i] = new int[n];
	G = G-1; for(int i=1;i<=n;i++) G[i] = G[i]-1;
	color = new string[n]; color = color-1;

	for(int i=1;i<=n;i++){
		for(int j=1;j<=n;j++) cin>>G[i][j];
	}

	cout<<prim()<<endl;

	delete [] (d+1); delete [] (p+1);
	for(int i=1;i<=n;i++) delete [] (G[i]+1); delete [] (G+1);
	delete [] (color+1);
}

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

	while(1){
		int u , mincost = Infty;
		for(int i=1;i<=n;i++){
			if(color[i]!="BLACK"&&d[i]<mincost){
				mincost = d[i];
				u = i;
			}
		}

		if(mincost==Infty) break;

		color[u] = "BLACK";

		for(int v=1;v<=n;v++){
			if(color[v]!="BLACK" && G[u][v]!=-1){
				if(G[u][v]<d[v]){
					d[v] = G[u][v];
					p[v] = u;
					color[v] = "GRAY";
				}
			}
		}
	}

	int sum = 0;
	for(int i=1;i<=n;i++){
		sum += d[i];
	}
	return sum;
}

C++: #include <iostream>
using namespace std;
static const int MAX = 100;
static const int INF = (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;
  // d: TとT-Vをつなぐ重みが最小の辺の重み
  // p: p[v]に頂点vの親
  int d[MAX], p[MAX], color[MAX];

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

  d[0] = 0;

  while (1) {
    minv = INF;
    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] != 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;
}

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) ? INF : e;
    }
  }

  cout << prim() << endl;
}