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 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]; // d:??±??? ,p:??????v?????? ,color:????????????

  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++: #include <iostream>
#include <set>
using namespace std;

const int Max = 105;
const int INF = (1<<29);
int n, G[Max][Max], Min;
set<int> T;
set<int> V;

void Pime0(int u)
{
    T.insert(u);
    V.erase(u);
    set<int>::iterator i, j;
    while(T.size()<n)
    {
        int minv = INF;
        int index = -1;
        for(i=T.begin(); i!=T.end(); i++)
        {
            for(j=V.begin(); j!=V.end(); j++)
            {
                if(G[*i][*j]!=INF && minv>G[*i][*j])
                {
                    minv = G[*i][*j];
                    index = *j;
                }
            }
        }
        T.insert(index);
        V.erase(index);
        Min += minv;
    }
}
int main()
{
    cin >> n;
    Min = 0;
    for(int i=0; i<n; i++)
    {
        V.insert(i);
    }
    for(int i=0; i<n; i++)
    {
        for(int j=0; j<n; j++)
        {
            cin >> G[i][j];
            if(G[i][j]==-1)
                G[i][j] = INF;
        }
    }
    Pime0(0);
    cout << Min << endl;
    return 0;
}

C++: #include<iostream>
#include<utility>
#include<algorithm>
using namespace std;
int p[101];
void makeset(int N){
    for(int i=0;i<N;++i){
        p[i]=i;
    }
}
int root(int x){
    if(p[x]==x) return x;
    return (p[x]==root(p[x]));
}
void unite(int x,int y){
    p[root(x)]=root(y);
}
bool same(int x,int y){
    return root(x)==root(y);
}
int main(){
    int N,M=0;
    int A[101][101],cost[101],src[101],dst[101];
    cin>>N;
    makeset(N);
    for(int r=0;r<N;++r){
        for(int c=0;c<N;++c){
            cin>>A[r][c];
        }
        for(int c=r+1;c<N;++c){
            if(A[r][c]>-1){
                cost[M]=A[r][c];
                src[M]=r;
                dst[M]=c;
                M+=1;
            }
        }
    }
    pair<int,pair<int,int>>edges[101];
    for(int i=0;i<M;++i){
       edges[i]=make_pair(cost[i],make_pair(src[i],dst[i]));
    }
    sort(edges,edges+M);
    //for(int i=0;i<M;++i){
        //cout<<edges[i].first<<edges[i].second.first<<edges[i].second.second<<endl;
    //}
    int total=0,num=0,flag=0;
    for(int i=0;i<M;++i){
        //if(same(edges[i].second.first,edges[i].second.second)){continue;}
        //else{
            unite(edges[i].second.first,edges[i].second.second);
            total+=edges[i].first;
            num++;
            cout<<edges[i].first<<edges[i].second.first<<edges[i].second.second<<endl;
        //}
        if(num==N-1){
            flag=1;
            break;
        }
    }
    if(flag){
        cout<<total<<endl;
    }
}

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 GREY = 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;
}