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 BLACK 0
#define GRAY 1
#define WHITE 2

int prim(int n, int **A, int *d, int *p) {
  int *color = new int[n];

  for (int i = 0; i < n; i++) {
    color[i] = WHITE;
    d[i] = INF;
  }

  d[0] = 0;
  p[0] = -1;

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

    if (mincost == INF) {
      break;
    }

    color[u] = BLACK;

    for (int v = 0; v < n; v++) {
      if ((color[v] != BLACK) && (A[u][v] != INF)) {
        if (A[u][v] < d[v]) {
          d[v] = A[u][v];
          p[v] = u;
          color[v] = GRAY;
        }
      }
    }

  }

  delete color;

  return 0;
}

int main() {
  int n;
  cin >> n;

  int **A = new int*[n];
  for (int i = 0; i < n; i++) {
    A[i] = new int[n];
  }

  for (int i = 0; i < n; i++) {
    for (int j = 0; j < n; j++) {
      int w;
      cin >> w;
      if (w == -1) {
        A[i][j] = INF;
      }
      else {
        A[i][j] = w;
      }
    }
  }

  int *d = new int[n];
  int *p = new int[n];
  prim(n, A, d, p);

  int sum = 0;
  for (int i = 0; i < n; i++) {
    sum += d[i];
  }

  cout << sum << endl;

  for (int i = 0; i < n; i++) {
    delete[] A[i];
  }
  delete[] A;

  delete d;
  delete p;

  return 0;
}

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

using namespace std;

struct Path{
    int w,s,t;
    
    bool operator < (const Path &a) const{
        return w < a.w;
    }
};

struct UnionFind{
    vector<int> par;
    
    UnionFind(int n)
        :par(n)
    {
        for(int i=0;i<n;i++){
            par[i]=i;
        }
    }
    
    void unite(int x,int y){
        int rx=root(x),ry=root(y);
        if(rx==ry)return;
        else{
            par[rx]=ry;
            return;
        }
    }
    
    int root(int x){
        if(x==par[x])return x;
        else return par[x]=root(par[x]);
    }
};

int main(void){
    int i,j,n,w;
    vector<Path> path;
    Path tmp;
    
    cin>>n;
    for(i=0;i<n;i++){
        for(j=0;j<n;j++){
            cin>>w;
            if(i>j)continue;
            else if(w!=-1){
                tmp.w=w,tmp.s=i,tmp.t=j;
                path.push_back(tmp);
            }
        }
    }
    
    sort(path.begin(),path.end());
    
    UnionFind tree(n);
    int sum=0;

    for(i=0;i<path.size();i++){
        tmp=path[i];
        if(tree.root(tmp.s)!=tree.root(tmp.t)){
            tree.unite(tmp.s,tmp.t);
            sum+=tmp.w;
        }
    }

    cout<<sum<<endl;
    return 0;
}

C++: //最少全域木
#include<iostream>
#include<vector>
#include<algorithm>
using namespace std;
int G[103][103];
int V;
int NG[103][103];//新しくできるほう
int used[103];
int main(){
	int ans=0;
	cin>>V;
	for(int i=0;i<V;i++){
		for(int j=0;j<V;j++){
		cin>>G[i][j];
		}
	}
	for(int i=0;i<103;i++)for(int j=0;j<103;j++)NG[i][j]=-1;
	used[0]=1;
	for(int i=0;i<V;i++){
		int u=-1,a,b;
		for(int j=0;j<V;j++){
		if(used[j]==0)u=i;
		}
		if(u==-1)break;
		int now=99999999;
		for(int j=0;j<V;j++){
			for(int k=0;k<V;k++){
			if(now>G[j][k]&&G[j][k]!=-1&&used[j]==1&&used[k]==0){
			now=G[j][k];
			a=j,b=k;
			}
			}
		}
		ans+=G[a][b];
		used[b]=1;
		NG[a][b]=G[a][b];
	}
	cout<<ans<<endl;
	return 0;
}