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;

typedef pair< int , int > P;
struct Edge {
  int to,cost;
  Edge(){}
  Edge(int to,int cost):to(to),cost(cost){};
};
vector< vector< Edge > > Graph;
int V,E;
int prim(){
  int total = 0;
  vector< bool > used(Graph.size(),false);
  priority_queue< P,vector< P >,greater< P > > que;
  que.push(P(0,0));
  while(!que.empty()){
    int cost = que.top().first;
    int now = que.top().second;
    que.pop();
    if(used[now]) continue;
    used[now] = true;
    total += cost;
    for(int i=0;i<Graph[now].size();i++){
      que.push(P(Graph[now][i].cost,Graph[now][i].to));
    }
  }
  return total;
}

int main(){
  cin >> V;
  Graph.resize(V+1);
  /*
  for(int i=0;i<E;i++){
    int s,t,d;
    cin >> s >> t >> d;
    Graph[s].push_back(Edge(t,d));
    Graph[t].push_back(Edge(s,d));
    }*/
  for(int i=0;i<V;i++){
    for(int j=0;j<V;j++){
      int d; cin >> d;
      if(d != -1){
	Graph[i].push_back(Edge(j,d));
	Graph[j].push_back(Edge(i,d));
      }
    }
  }
  cout << prim() << endl;
}

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

int main(){
  vector<vector<int> > graph;
  vector<int> master_node;
  vector<int> distance;
  vector<int> to_neighbor;
  int n;

  cin >> n;
  n++;
  graph.resize(n);
  master_node.resize(n);
  distance.resize(n);
  to_neighbor.resize(n);
  for(int i=1;i<n;i++){
    graph[i].resize(n);
    master_node[i]=0;
    distance[i]=INT_MAX;
    to_neighbor[i]=INT_MAX;
  }

  for(int i=1;i<n;i++){
    for(int j=1;j<n;j++){
      int input;

      cin >> input;
      graph[i][j]=(input!=-1?input:INT_MAX);
    }
  }


  int from=1;

  master_node[1]=1;
  distance[1]=0;
  for(int i=1;i<n;i++){
    to_neighbor[i]=(graph[1][i]<to_neighbor[i]?graph[1][i]:to_neighbor[i]);
  }
  while(true){
    int min_distance=INT_MAX,to;

    for(int i=1;i<n;i++){
      if((to_neighbor[i]<min_distance)&&(master_node[i]==0)){
        min_distance=to_neighbor[i];
	to=i;
      }
    }
    if(min_distance==INT_MAX){
      break;
    }else{
      master_node[to]=from;
      distance[to]=min_distance;
      from=to;
      to_neighbor[from]=INT_MAX;
      for(int i=1;i<n;i++){
        to_neighbor[i]=(graph[from][i]<to_neighbor[i]?graph[from][i]:to_neighbor[i]);
      }
    }
  }


  int sum=0;
  
  for(int i=1;i<n;i++){
    sum+=distance[i];
  }
  cout << sum << endl;
}

C++: #include<iostream>
#include<iomanip>
#include<algorithm>
#include<bitset>
#include<cctype>
#include<cmath>
#include<cstdio>
#include<cstring>
#include<functional>
#include<limits>
#include<list>
#include<map>
#include<set>
#include<stack>
#include<string>
#include<sstream>
#include<queue>
#include<vector>
using namespace std;

#define MOD 1000000007
#define INF 0x3f3f3f3f
#define INFL 0x3f3f3f3f3f3f3f3fLL

#define MAX 100
#define WHITE 0
#define GRAY 1
#define BLACK 2

int n, M[MAX][MAX];

int prim() {
	int d[MAX],
		p[MAX] = { -1 },
		color[MAX] = {};//WHITE
	fill(d, d + MAX, INF);
	d[0] = 0;

	while (true) {
		int u, minv = INF;
		for (int i = 0; i < n; i++) {
			if (color[i] != BLACK&&d[i] < minv) {
				minv = d[i];
				u = i;
			}
		}

		if (minv == INF) { break; }

		color[u] = BLACK;

		for (int v = 0; v < n; v++) {
			if (color[v] != BLACK&&M[u][v] != INF) {
				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() {
	cin >> n;
	for (int i = 0; i < n; i++) {
		for (int j = 0; j < n; j++) {
			int a; cin >> a;
			M[i][j] = (a == -1) ? INF : a;
		}
	}

	cout << prim() << endl;

	return 0;
}

C++: #include <iostream>
#include <climits>
#include <queue>

using namespace std;
static const int MAX=100;
static const int WHITE=1;
static const int GRAY=2;
static const int BLACK=3;

int n,M[MAX+10][MAX+10];

int prim()
{
    int u,minv;
    int d[MAX],p[MAX],color[MAX];

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

    d[0]=0;

    while(1)
    {
        minv=INT_MAX;
        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]!=INT_MAX)
        {
            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++)
      for(int j=0;i<n;j++)
    {
        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)? INT_MAX:e;
    }

    cout<<prim()<<endl;
    return 0;
}