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>
#include<algorithm>
using namespace std;

#define INF 2000

int n;
int cost[110][110], mincost[110];
bool used[110];

int prim(){

  //initialization
  for(int i = 0;i < n;i++){
    mincost[i] = INF;
    used[i] = false;
  }

  //cost of starting position is 0
  mincost[0] = 0;
  int ans = 0;
  
  while(true){
    int v = -1;
    
    for(int u = 0;u < n;u++){
      if(!used[u] && (v == -1 || mincost[u] < mincost[v])) v = u;
    }

    if(v == -1) break; //finish
    used[v] = true; //use v
    ans += mincost[v];

    //update mincost
    for(int u = 0;u < n;u++){
      mincost[u] = min(mincost[u], cost[v][u]);
    }
  }
  
  return ans;
}

int main(){

  //input
  cin >> n;
  for(int i = 0;i < n;i++){
    for(int j = 0;j < n;j++){
      cin >> cost[i][j];
      if(cost[i][j] == -1) cost[i][j] = INF;
    }
  }

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

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

const int MAX = 100;

struct Edge {
	Edge(int v1, int v2, int cost) :v1(v1), v2(v2), cost(cost) {};
	bool operator < (const Edge& e) const {
		return cost > e.cost;
	}
	int v1;
	int v2;
	int cost;
};

int parent(int uft[], int c) {
	if (uft[c] == -1)return c;
	return uft[c] = parent(uft, uft[c]);
}

int main() {
	int n;
	int uft[MAX];
	int sum = 0;
	priority_queue<Edge> q;
	
	cin >> n;

	for (int i = 0; i < n; i++) {
		uft[i] = -1;
	}

	for (int i = 0; i < n; i++) {
		for (int j = 0; j < n; j++) {
			int temp;
			cin >> temp;
			if (temp != -1){
				Edge e(i, j, temp);
				q.push(e);
			}
		}
	}

	while (!q.empty()) {
		Edge e = q.top(); q.pop();
		int p1 = parent(uft, e.v1);
		int p2 = parent(uft, e.v2);

		if (p1 != p2) {
			uft[p1] = p2;
			sum += e.cost;
		}
	}

	cout << sum << endl;
}

C++: #include<iostream>
#define MAX 101
#define INF (2<<29)
using namespace std;
int main(){
  int n;
  cin>>n;
  int graph[MAX][MAX];
  
  for(int i=1;i<n+1;i++){
    for(int j=1;j<n+1;j++){
      cin>>graph[i][j];
      if(graph[i][j]==-1)graph[i][j]=INF;
    }
  }
  
  int visited[MAX];
  int min[MAX];
  for(int i=1;i<n+1;i++){
    visited[i]=0;
    min[i]=INF;
  }
  
  min[1]=0;
  int ans=0;
  while(true){
    int a=-1;
    for(int i=1;i<n+1;i++){
      if(visited[i]==0&&(a==-1||min[i]<min[a]))a=i;
    }

    if(a==-1)break;
    visited[a]=1;
    ans +=min[a];

    for(int i=1;i<n+1;i++){
      min[i]=min[i]<graph[a][i] ? min[i]:graph[a][i];
    }
  }
  cout<<ans<<endl;
  return 0;
}

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

struct edge {
	int x;
	int y;
	int cost;
	edge(int x, int y, int cost) { this->x = x; this->y = y; this->cost = cost; }
};

bool operator<(const edge& e, const edge& f) { return e.cost < f.cost; }
bool operator<=(const edge& e, const edge& f) { return e.cost <= f.cost; }
bool operator>(const edge& e, const edge& f) { return e.cost > f.cost; }
bool operator>=(const edge& e, const edge& f) { return e.cost >= f.cost; }
bool operator==(const edge& e, const edge& f) { return e.cost == f.cost; }
bool operator!=(const edge& e, const edge& f) { return e.cost != f.cost; }

int root(int* par, int x)
{
	if (par[x] == x) return x;
	else return root(par, par[x]);
}
	
bool isSame(int* par, int x, int y)
{
	return root(par, x) == root(par, y);
}

void unite(int* par, int x, int y)
{
	if (!isSame(par, x, y)) par[root(par, x)] = root(par, y);
}

int main()
{
	int n; std::cin >> n;
	
	int *par = new int[n];
	for (int i=0; i<n; i++) par[i] = i;
	
	std::vector<edge> edge_list;
	
	for (int i=0; i<n; i++) {
		for (int j=0; j<n; j++) {
			int cost;
			std::cin >> cost;
			if (i < j && cost >= 0) edge_list.push_back( edge(i, j, cost) );
		}
	}
	
	std::sort(edge_list.begin(), edge_list.end());
	
	int totalcost = 0;
	int num_of_edges = 0;
	for (std::vector<edge>::iterator it = edge_list.begin(); it != edge_list.end(); ++it) {
		if (isSame(par, (*it).x, (*it).y)) continue;
		unite(par, (*it).x, (*it).y);
		totalcost += (*it).cost;
		num_of_edges++;
		// std::cout << (*it).x << "," << (*it).y << " " << (*it).cost << std::endl;
		if (num_of_edges == n-1) break;
	}
	
	std::cout << totalcost << std::endl;

	delete[] par;
	
	return 0;
}