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 <iostream>

using namespace std;
static const int MAX=100;
static const int INF=1<<21;

int p[MAX]; //????°???????????????????????????¶??????
int d[MAX]; //??????????¨??????????????????????????????????????????????
int M[MAX][MAX]; //u???v????????????
bool visited[MAX]; //??????????¢??????\

int prim(int n)
{
    //init
    for(int i=0;i<n;i++)
    {
        p[i]=-1;
        visited[i]=false;
        d[i]=INF; //????§???????????????????d?????????????????§
    }

    d[0]=0; //?¬¬0?????????d?????´??°
    while(true)
    {
        //??????d???????°????????????\??????
        int min=INF;
        int min_point=-1;
        for(int i=0;i<n;i++)
        {
            if(d[i]<min&&visited[i]==false)
            {
                min_point=i;
                min=d[i];
            }
        }
        if(min==INF) break;
        visited[min_point]=true;
        //??´??°???????????°?????\????????????????????????d???
        for(int i=0;i<n;i++)
        {
            if(M[min_point][i]!=INF&&visited[i]==false)
                if(d[i]>M[min_point][i])
                {
                    d[i] = M[min_point][i]; //??????d????????§????°±????????´??°
                    p[i]=min_point; //??????
                }
        }
    }
    int sum=0;
    for(int i=0;i<n;i++)
        if(p[i]!=-1) //??????????°?????????????????????¶
           sum+=M[i][p[i]];
    return sum;
}

int main()
{
    int n;
    cin>>n;
    for(int i=0;i<n;i++)
    {
        for(int j=0;j<n;j++)
        {
            cin>>M[i][j];
            M[i][j]=(M[i][j]==-1?INF:M[i][j]);
        }
    }
    cout<<prim(n)<<endl;
}

C++: #include <iostream>

using namespace std;
int n;
int dat[100][100];
int cost[100];
int done[100];

void prim(){
	for(int i=0;i<n;i++){
		cost[i]=1<<21;
		done[i]=0;
	}
	int s=0;	
	int next, ncost=1<<21;
	done[s]=1;
	cost[s]=0;
	while(1){
		ncost=1<<21;
		for(int j=0;j<n;j++){
			if(done[j]){
				for(int i=0;i<n;i++){
					if(dat[j][i]!=-1){
						if(cost[i]>=dat[j][i]&&!done[i]){
							cost[i]=dat[j][i];
						}
						if(ncost>cost[i]&&!done[i]){
							next=i;
							ncost=cost[i];
						}
					}
				}
			}
		}
//		cout<<"next:"<<next<<" cost:"<<cost[next]<<endl;
		done[next]=1;
		int flag=true;
		for(int i=0;i<n;i++){
			if(!done[i]) flag = false;
		}
		if(flag)
			return;
	}
}


int main(){
	cin>>n;
	for(int i=0;i<n;i++){
		for(int j=0;j<n;j++){
			cin>>dat[i][j];
		}
	}
	prim();
	int sum=0;
	for(int i=0;i<n;i++){
		sum+=cost[i];
	}
	cout<<sum<<endl;
	return 0;
}

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

int P[10010];
void init(int N){
  for (int i=0; i<N; i++) P[i] = i;
}
int root (int a){
  if (P[a] == a) return a;
  else {
    P[a] = root(P[a]);
    return P[a];
  }
}
bool is_same_set(int a, int b){
  return root(a) == root(b);
}
void unite(int a, int b){
  P[root(a)] = root(b);
}

int main(){
  int N;
  cin >> N;
  pair <int, int> edge[10010];
  for (int i=0; i<N; i++){
    for (int j=0; j<N; j++){
      cin >> edge[i*N+j].first;
      edge[i*N+j].second = i*N+j;
    }
  }
  sort(edge, edge+N*N);
  init(N);
  int ans = 0;
  int b = 0;
  for (int k=0; k<N*N; k++){
    while(edge[k].first < 0) k++;
    int i = edge[k].second / N;
    int j = edge[k].second % N;
    if (is_same_set(i,j)){}
    else{
      unite(i,j);
      ans += edge[k].first;
    }
  }
  cout << ans << endl;
}

C++: #include<bits/stdc++.h>
#define REP(i,n) for(int i=0;i<(int)(n);i++)
using namespace std;

int N;
const int MAX_E=100;
int label[MAX_E];
priority_queue<int,vector<pair<int,pair<int,int> > >,greater<pair<int,pair<int,int> > > > pq;

int main(){
  cin>>N;
  REP(i,N)
    label[i]=i;
  REP(i,N){
    REP(j,N){
      int a;cin>>a;
      if(a>=0&&i>j){
	pq.push(make_pair(a,make_pair(j,i)));
      }
    }
  }
  int size=0;
  while(!pq.empty()){
    int cost=pq.top().first;
    pair<int,int> e=pq.top().second;
    pq.pop();
    if(label[e.first]!=label[e.second]){
      size+=cost;
      REP(i,N){
	if(label[i]==label[e.second])
	  label[i]=label[e.first];
      }
    }
  }
  printf("%d\n",size);
}

C++: #include "stdafx.h"
#include <iostream>
using namespace std;

int main(void)
{
	int n, now = 0, flag[101] = {};
	long ans = 0, an[100][100], min[100];

	cin >> n;

	for (int i = 0; i < n; i++) {
		for (int j = 0; j < n; j++)
			cin >> an[i][j];
		min[i] = 1000000000;
	}

	do {
		long key = LONG_MAX, key_i;
		flag[now] = 1;
		flag[100] = 0;

		for (int i = 0; i < n; i++) {
			if (an[now][i] != -1 && an[now][i] < min[i] && flag[i] == 0)
				min[i] = an[now][i];
			if (flag[i] == 0 && min[i] < key) {
				key = min[i];
				key_i = i;
			}
			if (flag[i] == 1)
				flag[100]++;
		}

		now = key_i;
		ans += key;

	} while (flag[100] != n - 1);

	cout << ans << endl;

	return 0;
}