Go: package main

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

const (
	white int = iota
	gray
	black
)
const INFTY int = 2001

var G [][]int
var color []int
var d []int
var p []int
var N int

func prim() int {
	u := 0
	d[u] = 0
	for {
		minCost := INFTY
		for i:=0; i<N; i++ {
			if color[i] != black && d[i] < minCost {
				minCost = d[i]
				u = i
			}
		}

		if minCost == INFTY {
			break
		}

		color[u] = black

		for v:=0; 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
				}
			}
		}
	}
	// sum
	sum := 0
	for i:=0; i<N; i++ {
		if p[i] != -1 {
			sum += G[i][p[i]]
		}
	}
	return sum
}




func initVariable(N int) {
	G = make([][]int, N)
	for i:=0; i<N; i++ {
		G[i] = make([]int, N)
	}
	color = make([]int, N)
	d = make([]int, N)
	p = make([]int, N)
	for i:=0; i<N; i++ {
		d[i] = INFTY
		p[i] = -1
	}
}

func nextInt(scanner *bufio.Scanner) int {
	scanner.Scan()
	num, _ := strconv.Atoi(scanner.Text())
	return num
}

func main() {
	scanner := bufio.NewScanner(os.Stdin)
	scanner.Split(bufio.ScanWords)
	N = nextInt(scanner)
	initVariable(N)
	for i:=0; i<N; i++ {
		for j:=0; j<N; j++ {
			G[i][j] = nextInt(scanner)
		}
	}
	fmt.Printf("%d\n", prim())
}

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++: //
// Created by tattsun on 2017/02/16.
//

#include <iostream>

#define MAX_N 101
#define INFTY 20000
#define NIL -1

enum Color {
    White,
    Glay,
    Black,
};

using namespace std;

int n;
int w[MAX_N][MAX_N];
int d[MAX_N], p[MAX_N];
Color color[MAX_N];

int min(int x, int y) {
    if(x < y) return x;
    return y;
}

int solve() {
    d[0] = 0;

    while(true) {
        int u = NIL, c = INFTY;

        for(int i=0; i<n; i++) {
            if(d[i] < c && color[i] != Black) {
                u = i;
                c = d[i];
            }
        }

        if(u == NIL)
            break;

        color[u] = Black;

        for(int i=0; i<n; i++) {
            if(color[i] != Black && w[u][i] != INFTY) {
                if(d[i] > w[u][i]) {
                    d[i] = w[u][i];
                    p[i] = u;
                    color[i] = Glay;
                }
            }
        }
    }


    int tc = 0;
    for(int i=0; i<n; i++) {
        if(color[i] == Black) {
            tc += w[i][p[i]];
        }
    }
    return tc;
}

int main() {
    for (int i = 0; i < MAX_N; i++) {
        d[i] = INFTY;
        p[i] = INFTY;
        color[i] = White;
        for (int j = 0; j < MAX_N; j++)
            w[i][j] = INFTY;
    }

    int p;
    cin >> n;
    for (int i = 0; i < n; i++) {
        for (int j = 0; j < n; j++) {
            cin >> p;
            w[i][j] = (p == -1) ? INFTY : p;
        }
    }

    cout << solve() << endl;
}

C++: #define _CRT_SECURE_NO_WARNINGS
#define _USE_MATH_DEFINES
#include <iostream>
using namespace std;
const int num = 100;
int v[num][num], n, c[num], p[num], d[num];;
inline int mini(int k) {
	for (int i = 0; i < n; i++) {
		d[i] = 99999999;
	}

	d[k] = 0;
	p[k] = -1;
	while (1) {
		int minv = 99999999, u = -1;
		for (int i = 0; i < n; i++) {
			if (d[i] < minv && c[i] == 0) {
				minv = d[i];
				u = i;
			}
		}
		if (u == -1) break;
		for (int i = 0; i < n; i++) {
			if (v[u][i] != -1 && c[i] == 0) {
				if (d[i] > v[u][i]) {
					d[i] = v[u][i];
					p[i] = u;
				}
			}
		}
		c[u] = 1;
	}
	int sum = 0;
	for (int i = 0; i < n; i++) {
		if(p[i] != -1) sum += v[i][p[i]];
	}
	return sum;
}
int main() {
	cin >> n;
	for (int i = 0; i < n; i++) {
		for (int j = 0; j < n; j++) {
			cin >> v[i][j];
		}
	}
	for (int i = 0; i < n; i++) {
		c[i] = 0;
	}
	cout << mini(0) << endl;
	return 0;
}

C++: #include <algorithm>
#include <iostream>
#include <set>
#include <vector>
#define FOR(i,k,n) for (int (i)=(k); (i)<(n); ++(i))
#define REP(i,n) FOR(i,0,n)
#define pb push_back
#define mp make_pair
#define fst first
#define snd second
#define all(v) begin(v), end(v)
using namespace std;
typedef pair<int,int> PII;

int P[100]; //union_find

int root(int i){
    if(P[i] == i) return i;
    else return P[i] = root(P[i]);
}

bool same(int x, int y){
    return root(P[x]) == root(P[y]);
}

void unite(int x, int y){
    P[root(x)] = root(y);
}

int main(){
    int n;
    cin >> n;
    int g[n][n];
    vector<pair<int,PII>> V;
    REP(i,n){
        REP(j,n){
            cin >> g[i][j];
            if(i<j && g[i][j] >= 0) V.pb(mp(g[i][j],mp(i,j)));
        }
    }
    sort(all(V));
    REP(i,n){
        P[i] = i;
    }
    int wsum=0;
    REP(i,n-1){
        int x = V[i].snd.fst;
        int y = V[i].snd.snd;
        if(!same(x,y)){
            unite(x,y);
            wsum += V[i].fst;
        }
    }

    cout <<wsum<<endl;

    return 0;
}

C++: #include<stdio.h>

static const int MAX = 500;
static const int INFTY = (1<<21);

main(){
  int n, i, j, e, sum,M[MAX][MAX]={0};
  int u,minV,INT_MAX,A[MAX]={INFTY},key[MAX]={INFTY};
  /*

    your code


   */

  scanf("%d", &n);
  
  for ( i = 0; i< n; i++ ){
    for ( j = 0; j < n; j++ ){
      scanf("%d", &e);
      M[i][j] = (e==-1)?INFTY:e;
    }
  }
  
  
  while(1){
    minV = 
      for(i=1;i<=n;i++){
        if((i < minV) && 

  






















  sum = 0;

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

  printf("%d\n", sum);

  return 0;
}

C++: #include <iostream>
using namespace std;
static const int MAX = 10;
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;
}