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;
#define INF 1<<21
#define WHITE 0
#define GRAY 1
#define BLACK 2
#define MAX 100

int v_num;
int adjM[MAX+1][MAX+1];

int PrimsAlgorithm() 
{
    int current_vertex;
    int color[v_num+1], min_edge[v_num+1], parent[v_num+1];

    // set init state
    for (int i = 0; i < v_num; ++i)
    {
        color[i] = WHITE;
        min_edge[i] = INF;
        parent[i] = -1;
    }

    min_edge[0] = 0;

    while (true) 
    {
        int min_cost = INF;
        // move to the minimum vertex which can be accessed 
        for (int i = 0; i < v_num; ++i) 
        {
            if (color[i] != BLACK && min_edge[i] < min_cost)
            {
                min_cost = min_edge[i];
                current_vertex = i;
            }
        }

        if (min_cost == INF) break;

        color[current_vertex] = BLACK;

        for (int i = 0; i < v_num; ++i) 
        {
            if (color[i] != BLACK && adjM[current_vertex][i] != -1)
            {
                if (adjM[current_vertex][i] < min_edge[i])
                {
                    min_edge[i] = adjM[current_vertex][i];
                    parent[i] = current_vertex;
                    color[i] = GRAY;
                }
            } 
        }
    }

    int sum = 0;
    for (int i = 0; i < v_num; ++i) 
    {
        if (parent[i] != -1) sum += adjM[i][parent[i]];
    }
    return sum;
}

int main() 
{
    int v;
    cin >> v_num;
    for (int i = 0; i < v_num; ++i) 
    {
        for (int j = 0; j < v_num; ++j)
        {
            cin >> v;
            adjM[i][j] = v != -1 ? v : INF;
        }
    }
    
    cout << PrimsAlgorithm() << endl;
}

C++: #include <iostream>

using namespace std;


class Graph{
private:

  int size;
  int **graph;
  int *state;

public:

  Graph(int size){
    int i;
    int j;
    this->size = size;
    this->state = new int[size];
    this->graph = new int*[size];
    for(i = 0;i < size;i++){
      this->graph[i] = new int[size];
    }
    for(i = 0;i < this->size;i++){
	this->state[i] = 0;
      }
  }

  ~Graph(){
    int i;
    for(i = 0;i < this->size;i++){
      delete[] this->graph[i];
    }
    delete[] this->graph;
  }

  int getMinimum(){
    int i;
    int j;
    int min;
    int res = 0;

    for(i = 0;i < this->size;i++){
      min = 0;

      for(j = 1;j < this->size;j++){
	if(this->graph[i][j] != -1 && this->state[j] == 0){
	  if(this->graph[i][j] <= this->graph[i][min] 
	     ||	this->graph[i][min] == -1){
	    min = j;
	  }
	}
      }

      if(state[min] == 0){
	state[min] = 1;
	res += graph[i][min];
      }
    }
    return res;
  }

  void setValue(int x,int y,int value){
    this->graph[x][y] = value;
  }

};

int main(){

  int i;
  int j;
  int n;
  int a;

  Graph *graph;

  cin >> n;

  graph = new Graph(n);

  for(i = 0;i < n;i++){
    for(j = 0;j < n;j++){
      cin >> a;
      graph->setValue(i,j,a);
    }
  }

  cout << graph->getMinimum() << endl;

  delete graph;

  return 0;
}

C++: #include <iostream>
#define NMAX 100
#define AMAX 2001

using namespace std;

enum state{
  WHITE,
  BLACK
};

int main(){
  int A[NMAX][NMAX];
  int n; cin>>n;
  state s[NMAX];
  
  for(int r=0;r<n;r++){
    for(int c=0;c<n;c++){
      cin>>A[r][c];
      if(A[r][c]==-1) A[r][c]=AMAX;
    }
  }

  for(int i=0;i<n;i++) s[i]=WHITE;
  s[0]=BLACK;
  
  int sum=0;

  while(1){
    bool flag=true;
    for(int i=0;i<n;i++){
      if(s[i]!=BLACK) flag=false;
    }
    if(flag) break;

    int min=AMAX;
    int minr,minc;
    for(int r=0;r<n;r++){
      for(int c=0;c<n;c++){
        if(s[r]==BLACK && s[c]!=BLACK && A[r][c]<min){
          min=A[r][c];
          minr=r;minc=c;
        }
      }
    }
    s[minr]=BLACK;s[minc]=BLACK; 
    sum+=min;
  }
  cout<<sum<<endl;
}

C++: #include<iostream>
#include<vector>

int main() {
	int num;
	std::cin >> num;

	std::vector<std::vector<int> > v(num);

	for (int i = 0; i < num; i++) {
		for (int j = 0; j < num; j++) {
			int n;
			std::cin >> n;
			v[i].push_back(n);
		}
	}

	std::vector<int> n(v.size(), 0);
	std::vector<int> color(v.size(), 0);
	int count = 0, color_count = 1;
	for (int i = 1; i <= 2000; i++) {
		for (size_t j = 0; j < v.size(); j++) {
			for (size_t k = 0; k < v.size(); k++) {
				if (v[j][k] == i && ((color[k] == 0 || color[j] == 0) || (color[k] != color[j]))) {
					if (color[k] == 0) {
						if (color[j] != 0) {
							color[k] = color[j];
						} else {
							color[k] = color[j] = color_count;
							color_count++;
						}
					} else {
						if (color[j] == 0) {
							color[j] = color[k];
						} else {
							for (int l = 0; l < color.size(); l++) {
								if (color[l] == color[j]) {
									color[l] = color[k];
								}
							}
						}
					}
					count += i;
				}
			}
		}
	}

	std::cout << count << std::endl;

	return 0;
}