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>
using namespace std;

#define INF 100000000

//訪問状態
#define White 0
#define Gray 1
#define Black 2

//Treeの状態を表した隣接行列
int Tree[100][100];
int sum = 0;

int prim(int n){
  int u, minv;
  //d = 見て来たノードの中から出る最小の辺を記録
  //p = MSTにおける頂点の親を記録
  int d[100], p[100], color[100];

  for(int i = 0 ; i < n ; i++){
    d[i] = INF;
    p[i] = -1;
    color[i] = White;
  }

  d[0] = 0;

  while(1){
    minv = INF;
    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 && Tree[u][v] != INF){
	if(d[v] > Tree[u][v]){
	  d[v] = Tree[u][v];
	  p[v] = u;
	  color[v] = Gray;
	}
      }
    }
  }

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

  return sum;

}

int main(){
  int n, status;

  cin >> n;

  for(int i = 0 ; i < n ; i++){
    for(int j = 0 ; j < n ; j++){
      cin >> status;

      if(status == -1){
	Tree[i][j] = INF;
      }else{
	Tree[i][j] = status;
      }
    }
  }

  cout << prim(n) << endl;

  return 0;
}

C++: #include <bits/stdc++.h>
using namespace std;
static const int INFTY = 2000000000;
static const int NIL = -1;
static const int MAX = 100;
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;   //d[i]??????T??????????????§?????????V????±?????????????i?????????????????????
        p[i] = NIL;
        color[i] = WHITE;
    }

    d[0] = 0;

    while(1){
        minv = INFTY;
        u = NIL;
        for(int i=0;i<n;i++){
            if(d[i] < INFTY && color[i] != BLACK){    //?¢????????????§????????????????????????INFTY??§?????????????????¢???
                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){  //2??????????????¶???????????????????
                if(M[u][v] < d[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(){
    scanf("%d",&n);

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

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

    return 0;
}

C++: #include <bits/stdc++.h>

using namespace std;

#define rep(i, n) for (int i = 0; i < (int)(n); i++)
#define all(v) v.begin(),v.end()
#define _GLIBCXX_DEBUG

using ll = long long;
using vi = vector<int>;
using vll = vector<ll>;
using vd = vector<double>;
using vvi = vector<vi>;
using vvll = vector<vll>;
using vvd = vector<vd>;
using vvvi = vector<vvi>;
using vvvll = vector<vvll>;
using vvvd = vector<vvd>;

const double pi=acos(-1);
const ll MOD=1e9+7;
const ll INF=(1LL<<60);

int cost[101][101];
int mincost[101];
int used[101];
int v;

int prim(){
    for (int i=0;i<v;i++){
        mincost[i]=1e9;
        used[i]=0;
    }
    mincost[0]=0;
    int res=0;
    while(1){
        int v1=-1;
        for (int u=0;u<v;u++){
            if (!used[u] && (v1==-1||mincost[u]<mincost[v1]))v1=u;
        }
        if (v1==-1)break;
        used[v1]=1;
        res+=mincost[v1];
        for (int u=0;u<v;u++)mincost[u]=min(mincost[u],cost[v1][u]);
    }
    return res;
}

int main() {
    cin>>v;
    rep(i,v){
        rep(j,v){
            cin>>cost[i][j];
            if (cost[i][j]==-1)cost[i][j]=1e8;
        }
    }
    int ans=0;
    ans=prim();
    cout<<ans<<endl;
    

    return 0;
}