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(shortestList)
	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++: /*
** prim for MST
*/

# include <iostream>
using namespace std;

static const int MAX = 100;
static const int INFTY = (1 << 21);
static const int WHITE = 0;
static const int GREY = 1;
static const int BLACK = 2;

int n, M[MAX][MAX];

void init() {
    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;
        }
    }
}

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

        if (minv == INFTY)
            break;

        color[u] = BLACK;

        for (int v = 0; v < n; v++) {
            if (color[v] != BLACK && M[u][v] != INFTY) {
                if (M[u][v] < d[v]) {
                    d[v] = M[u][v];
                    p[v] = u;
                    color[v] = GREY;
                }
            }
        }
    }

    int sum = 0;
    for (int i = 0; i < n; i++) {
        if (p[i] != -1) {
            sum += M[i][p[i]];
        }
    }

    return sum;
}

void solve() {
    init();
    cout << prim() << endl;
}

int main() {
    // freopen("infile", "r", stdin);
    // freopen("outfile", "w", stdout);
    solve();
    return 0;
}

C++: #include<bits/stdc++.h>
using namespace std;


class UnionFind{
    int N;
    vector<int> par;
    vector<int> rank;
    public:
    UnionFind(int N):N(N),par(N),rank(N,0){iota(par.begin(),par.end(),0);}
    int find(int x);
    void unite(int x,int y);
    bool same(int x,int y){return find(x)==find(y);}
};

int UnionFind::find(int x){
    if(par[x]==x) return x;
    return par[x]=find(par[x]);
}
void UnionFind::unite(int x,int y){
    x=find(x),y=find(y);
    if(x==y) return;
    if(rank[x]>=rank[y]){
        if(rank[x]==rank[y]) rank[x]++;
        par[y]=x;
    }else{
        par[x]=y;
    }
}

using Weight=long long;
struct Edge{
    int from,to;
    Weight weight;
};
bool operator<(const Edge& lhs,const Edge& rhs){
    return lhs.weight<rhs.weight;
}

using Edges=vector<Edge>;
using Graph=vector<Edges>;


Edges MinimumSpanningTree(int n,Edges edges){
    Edges res;
    UnionFind u(n);
    for(int i=0;i<edges.size();i++){
        if(!u.same(edges[i].from,edges[i].to)){
            res.push_back(edges[i]);
            u.unite(edges[i].from,edges[i].to);
        }
    }
    return res;
}

Edges MinimumSpanningTree(const Graph& g){
    Edges edges;
    for(int i=0;i<g.size();i++){
        copy(g[i].begin(),g[i].end(),back_inserter(edges));
    }
    auto res=MinimumSpanningTree(g.size(),edges);
    return res;
}

int main(){
    int n;
    cin>>n;
    Graph g(n);
    for(int i=0;i<n;i++){
        for(int j=0;j<n;j++){
            Weight c;
            cin>>c;
            if(a[i][j]==-1) continue;
            g[i].push_back({i,j,c});
        }
    }
    auto mst=MinimumSpanningTree(g);
    cout<<accumulate(mst.begin(),mst.end(),Weight(0),[](const Weight& lhs,const Edge& rhs){return lhs+rhs.weight;})<<endl;
    return 0;
}

C++: #include<iostream>
#include<cstdio>
#include<cstring>
#include<map>
#include<vector>
#include<queue>
using namespace std;

struct Edge{
  int src,dst;
  int weight;
  Edge(int src,int dst,int weight):
    src(src),dst(dst),weight(weight){}
};

typedef vector<Edge> Edges;
typedef vector<Edges> Graph;

bool operator < (const Edge &m,const Edge &n){
  return m.weight!=n.weight ? m.weight>n.weight :
    m.src!=n.src ? m.src>n.src : m.dst>n.dst;
}

struct UnionFind{
  vector<int> data;
  UnionFind(int size):
    data(size,-1){}

  int root(int x){
    return data[x]<0 ? x :
      data[x]=root(data[x]);
  }

  void unionset(int x,int y){ //bool->void
    x=root(x);y=root(y);
    if(x!=y){
      if(data[y]<data[x])
	swap(x,y);
      data[x]+=data[y];
      data[y]=x;
    }
    //return x!=y;
  }

  bool findset(int x,int y){
    return root(x)==root(y);
  }
};

pair<int,Edges> MinimumSpinningForest(Graph g){
  int n=g.size();
  UnionFind uf(n);
  priority_queue<Edge> que;

  for(int i=0;i<n;i++){
    for(Edges::iterator l=g[i].begin();l!=g[i].end();l++){
      if(i<(*l).dst)
	que.push(*l);
    }
  }

  int sum=0;
  Edges select;

  while((int)select.size()<n-1 && !que.empty()){
    Edge tmp=que.top();que.pop();

    if(!uf.findset(tmp.src,tmp.dst)){
      uf.unionset(tmp.src,tmp.dst);
      select.push_back(tmp);
      sum+=tmp.weight;
    }
  }

  return pair<int,Edges>(sum,select);
}

int main(int argc,char* argv[]){
  Graph g;
  int n,x;
  pair<int,Edges> p;

  cin>>n; 
  for(int i=1;i<=n;i++){
    for(int l=1;l<=n;l++){
      cin>>x;
      Edge tmp(i,l,x);
      Edges input;input.push_back(tmp);
      g.push_back(input);
    }
  }

  p=MinimumSpinningForest(g);

  cout<<p.first<<endl;
  return 0;
}