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 <stdio.h>
#define MAX 1 << 22
int map[1000][1000];
int n, minval = 999999;

int prim()
{
    int sum = 0;
    int d[1000], fathernode[1000], color[1000];;
    for(int i = 0; i < n; i ++)
        d[i] = fathernode[i] = MAX;
    d[0] = 0;
    while(true)
    {
        int ch = -1, min = MAX;
        for(int i = 0; i < n; i ++)
        {
            if(min > d[i] && color[i] == 0) //选取未被染色的点
            {
                ch = i;
                min = d[i];
            }
        }
        if(ch == -1) //选完了，跳出
            break;
        color[ch] = 1;//选取这个点后染色
        for(int j = 0; j < n; j ++)//选取V-T中与T距离最近的节点
        {
            if(d[j] > map[ch][j] && color[j] == 0)
            {
                d[j] = map[ch][j];
                fathernode[j] = ch;//j节点的父节点是ch
            }
        }
    }
    //选取完毕，开始加起来
    for(int k = 0; k < n; k ++)//只加被染色（即被选中的）节点
    {
        if(fathernode[k] != MAX)//只加上有父节点的点
            sum += map[k][fathernode[k]];
    }
    return sum;
}

int main(void)
{
    scanf("%d", &n);
    for(int i = 0; i < n; i ++)
        for(int j = 0; j < n; j ++)
        {
            int t;
            scanf("%d", &t);
            map[i][j] = (t == -1 ? MAX : t);
        }
    printf("%d\n", prim() );
    return 0;
}

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 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 = 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<cstdio>
#include<queue>
#include<map>
using namespace std;
typedef pair< int, int > Pi;
int info[100][100];
bool used[100];

int prim(const int& V){
  priority_queue< Pi > que;
  que.push(Pi());
  int ret = 0;
  while(!que.empty()){
    Pi p = que.top(); que.pop();
    if(!~-p.first || used[p.second]++) continue;
    ret -= p.first;
    for(int i = 0; i < V; i++) que.push( Pi( -info[p.second][i], i));
  }
  return ret;
}

int main(){
  int N;
  scanf("%d", &N);
  for(int i = 0; i < N; i++){
    for(int j = 0 ; j < N ; j++){
      scanf("%d", &info[i][j]);
    }
  }
  printf("%d\n", prim(N));
}

C++: #include <iostream>
#include <algorithm>
#include <vector>
#include <utility>
#include <queue>

using namespace std;
 
int prim(vector<vector<pair<int, int> > >& G) {
	int cost = 0;
	const int N = G.size();
	vector<bool> used(G.size());
	priority_queue<pair<int, int>, vector<pair<int, int> >, greater<pair<int, int> > > pq;
	pq.push(make_pair(0, 0));
	while (!pq.empty()) {
		pair<int, int> p = pq.top(); pq.pop();
		int now = p.second;
		if (used[now]) continue;
		used[now] = true;
		cost += p.first;
		for (auto e : G[now])
			pq.push(make_pair(e.second, e.first));
	}
	return cost;
}

int main() {
	int n; cin >> n;
	vector<vector<pair<int, int> > > G(n);
	for (int i = 0; i < n; ++i) {
		for (int j = 0; j < n; ++j) {
			int a; cin >> a;
			if (a != -1) G[i].push_back(make_pair(j, a));
		}
	}
	cout << prim(G) << endl;

	return 0;
}