Go: package main

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

const (
	MAX_N      = 200
	MAX_WEIGHT = 2000
)

type Edge struct {
	start  int
	end    int
	weight int
}

type ShortestInfo struct {
	edges    []Edge
	shortest int
}

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

	n, err := nextInt(sc)
	if err != nil {
		panic(err)
	}

	shortestList := make([]ShortestInfo, n)
	for i := 1; i < n; i++ {
		shortestList[i] = ShortestInfo{edges: []Edge{}, shortest: MAX_N*MAX_WEIGHT + 1}
	}

	adjacentMatrix := make([][]int, n)
	for i := 0; i < n; i++ {
		adjacentMatrix[i] = make([]int, n)
		for j := 0; j < n; j++ {
			v, err := nextInt(sc)
			if err != nil {
				panic(err)
			}
			adjacentMatrix[i][j] = v
		}
	}

	mst([]int{1}, shortestList, adjacentMatrix)
	fmt.Println(calculateMinWeight(shortestList))
}

func calculateMinWeight(shortestList []ShortestInfo) int {
	visitedList := make([]bool, len(shortestList))
	visitedList[0] = true
	sumWeight := 0
	for !visitedAll(visitedList) {
		shortestInfo := shortestList[0]
		shortestList = shortestList[1:]
		edges := shortestInfo.edges
		for _, edge := range edges {
			if !visitedList[edge.end-1] {
				visitedList[edge.end-1] = true
				sumWeight += edge.weight
			}
		}
	}
	return sumWeight
}

func visitedAll(visitedList []bool) bool {
	for _, v := range visitedList {
		if !v {
			return false
		}
	}
	return true
}

func mst(nodeStack []int, shortestList []ShortestInfo, adjacentMatrix [][]int) {
	for len(nodeStack) > 0 {
		currentNode := nodeStack[0]
		nodeStack = nodeStack[1:]
		currentShortest := getShortest(currentNode, shortestList)
		adjacents := findAdjacents(currentNode, adjacentMatrix)
		for i := 0; i < len(adjacents); i++ {
			adj := adjacents[i]
			s := getShortest(adj.end, shortestList)
			if currentShortest.shortest+adj.weight < s.shortest || (currentShortest.shortest+adj.weight == s.shortest && len(currentShortest.edges)+1 > len(s.edges)) {
				setShortest(adj.end, adj, currentShortest, shortestList)
				nodeStack = append(nodeStack, adj.end)
			}
		}
	}
}

func getShortest(node int, shortestList []ShortestInfo) ShortestInfo {
	return shortestList[node-1]
}

func setShortest(node int, edge Edge, currentShortest ShortestInfo, shortestList []ShortestInfo) {
	newEdges := make([]Edge, len(currentShortest.edges)+1)
	for i := 0; i < len(newEdges)-1; i++ {
		newEdges[i] = currentShortest.edges[i]
	}
	newEdges[len(newEdges)-1] = edge
	shortestInfo := ShortestInfo{edges: newEdges, shortest: currentShortest.shortest + edge.weight}
	shortestList[node-1] = shortestInfo
}

func findAdjacents(currentNode int, adjacentMatrix [][]int) []Edge {
	adjacents := adjacentMatrix[currentNode-1]
	edges := []Edge{}
	for i, v := range adjacents {
		if v > 0 {
			edges = append(edges, Edge{start: currentNode, end: i + 1, weight: v})
		}
	}
	return edges
}

func nextInt(sc *bufio.Scanner) (int, error) {
	sc.Scan()
	return strconv.Atoi(sc.Text())
}

C++: #include <bits/stdc++.h>
#define rep(i,a) for(i=0;i<a;i++)
using namespace std;
static const int W 0
static const int G 1
static const int B 2

void prim(int n, int *total, vector<vector<int> > &M) {
    int i,u,min;
    vector<int> d(n);
    vector<int> p(n);
    vector<int> color(n);

    rep(i,n){
        d[i] = INT_MAX;
        p[i] = -1;
        color[i] = INT_MAX;
    }
    d[0] = 0;
    while(true){
        min = INT_MAX;
        u = -1;
        rep(i,n){
            if(min > d[i] && color[i] != B) {
                u = i;
                min = d[i];
            }
        }
        if(u==-1) break;
        color[u] = B;
        rep(i,n){
            if(color[i] != B && M[u][i])
                if(d[i] > M[u][i]) {
                    d[i] = M[u][i];
                    p[i] = u;
                    color[u] = G;
                }
        }
    }
    rep(i,n){
        if(p[i] != -1) total += M[i][p[i]]
    }
}

int main(void) {
    int i,j,n,total = 0;
    vector<vector<int> > M;
    cin >> n;
    M.resize(n);

    rep(i,n){
        M[i].resize(n);
    }
    rep(i,n){
        rep(j,n){
            cin >> M[i][j];
            if(M[i][j] != -1) M[i][j] = INT_MAX;

        }
    }
    prim(n,&total,M);
    cout << total;
    return 0;
}

C++: #include <stdio.h>
#define INFTY 1000000
#define M -1
#define WHITE 0
#define GRAY  1
#define BLACK 2
#define N 100
int prim(void);
int n,A[N][N];

int main()
{
  int i,j,k;

  scanf("%d",&n);
  for(i=0;i<n;i++)
    {
      for(j=0;j<n;j++)
        {
          scanf("%d",&k);
          if(k==M) A[i][j]=INFTY;
        }
    }

  printf("%d\n",prim());
  return 0;
}

int prim()
{
  int d[N],p[N],color[N];
  int i,v,u,mincost,sum=0;

  for(i=0;i<n;i++)
    {
      d[i]=INFTY;
      p[i]=M;
      color[i]=WHITE;
    }
  d[0]=0;
while(1)
    {
      mincost=INFTY;
      u=M;
      for(i=0;i<n;i++)
        {
          if(color[i]!=BLACK&&d[i]<mincost)
            {
              u=i;
              mincost=d[i];
            }
        }
      if(u==M) break;
      color[u]=BLACK;
      for(v=0;v<n;v++)
        {
          if(color[v]!=BLACK&&A[u][v]!=INFTY)
            {
              if(d[v]>A[u][v])
                {
                  d[v]=A[u][v];
                  p[v]=u;
                  color[v]=GRAY;
                }
            }
        }
    }
  for(i=0;i<n;i++)
    {
      if(p[i]!=M) sum+=A[i][p[i]];
    }
  return sum;

C++: #include <iostream>
using namespace std;
int prim();
static const int maxs=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[maxs][maxs];

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;
}

int prim(){
  int u,minv;
  int d[maxs],p[maxs],color[maxs];
  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]];
  }
  // cout<<p[0]<<" "<<p[1]<<" "<<p[2]<<" "<<p[3]<<" "<<p[4]<<" "<<endl;/////////
  return sum;
}