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;
#define MAX 100
#define INFINITY (1<<30)
enum{
	white=0,
	gray=1,
	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]=INFINITY;
		p[i]=-1;
		color[i]=white;
	}
	d[0]=0;
	while(1){
		minv=INFINITY;
		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]!=INFINITY){
				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;
	int e;
	for(int i=0;i<n;i++){
		for(int j=0;j<n;j++){
			cin>>e;
			if(e==-1)	m[i][j]=INFINITY;
			else	m[i][j]=e;
		}
	}
	cout<<prim()<<endl;
	return 0;
}