Go: package main

import (
	"bufio"
	"fmt"
	"os"
	"strconv"
)

// I/O
type Scanner struct {
	sc *bufio.Scanner
}

func NewScanner() *Scanner {
	sc := bufio.NewScanner(os.Stdin)
	sc.Split(bufio.ScanWords)
	sc.Buffer(make([]byte, 1024), int(1e+9))
	return &Scanner{sc}
}

func (s *Scanner) nextStr() string {
	s.sc.Scan()
	return s.sc.Text()
}

func (s *Scanner) nextInt() int {
	i, e := strconv.Atoi(s.nextStr())
	if e != nil {
		panic(e)
	}
	return i
}

func (s *Scanner) nextFloat() float64 {
	f, e := strconv.ParseFloat(s.nextStr(), 64)
	if e != nil {
		panic(e)
	}
	return f
}

func (s *Scanner) nextRuneSlice() []rune {
	return []rune(s.nextStr())
}

func (s *Scanner) nextIntSlice(n int) []int {
	res := make([]int, n)
	for i := 0; i < n; i++ {
		res[i] = s.nextInt()
	}
	return res
}

func (s *Scanner) nextFloatSlice(n int) []float64 {
	res := make([]float64, n)
	for i := 0; i < n; i++ {
		res[i] = s.nextFloat()
	}
	return res
}

// Arithmetic
func max(nums ...int) int {
	m := nums[0]
	for _, i := range nums {
		if m < i {
			m = i
		}
	}
	return m
}

func min(nums ...int) int {
	m := nums[0]
	for _, i := range nums {
		if m > i {
			m = i
		}
	}
	return m
}

func abs(x int) int {
	if x > 0 {
		return x
	}
	return -x
}

func pow(x, y int) int {
	res := 1
	for i := 0; i < y; i++ {
		res *= x
	}
	return res
}

func ceil(a, b int) int {
	if a%b == 0 {
		return a / b
	} else {
		return a/b + 1
	}
}

// Sort
type RuneSlice []rune

func (a RuneSlice) Len() int           { return len(a) }
func (a RuneSlice) Less(i, j int) bool { return a[i] < a[j] }
func (a RuneSlice) Swap(i, j int)      { a[i], a[j] = a[j], a[i] }

const INF = 1 << 60

// Main
func main() {
	sc := NewScanner()
	wtr := bufio.NewWriter(os.Stdout)
	N := sc.nextInt()
	G := make([][]int, N)
	for i := 0; i < N; i++ {
		G[i] = make([]int, N)
		for j := 0; j < N; j++ {
			G[i][j] = sc.nextInt()
		}
	}
	d := make([]int, N)
	for i := 0; i < N; i++ {
		d[i] = INF
	}
	seen := make([]bool, N)
	d[0] = 0
	ans := 0
	for {
		cur := 0
		minCost := INF
		for i := 0; i < N; i++ {
			if !seen[i] && d[i] < minCost {
				minCost = d[i]
				cur = i
			}
		}
		if minCost == INF {
			break
		}
		seen[cur] = true
		ans += d[cur]
		for i := 0; i < N; i++ {
			cost := G[cur][i]
			if cost != -1 && cost < d[i] {
				d[i] = cost
			}
		}
	}

	fmt.Fprintln(wtr, ans)
	wtr.Flush()
}

C++: #include<iostream>

int prim();

using namespace std;
static const int MAX=100;
static const int INFTY=(1<<21);
static const int WHI=0;
static const int GRA=1;
static const int BLA=2;

int n,M[MAX][MAX];

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;
}

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]=WHI;
    }

  d[0]=0;

  while(1)
    {
      minv=INFTY;
      u=-1;
      for(int i=0;i<n;i++)
	{
	  if(minv>d[i]&&color[i]!=BLA)
	    {
	      u=i;
	      minv=d[i];
	    }
	}
      if(u==-1)
	break;

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

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

  return sum;
}

C++: #include <bits/stdc++.h>
using namespace std;
 
#define INF (1 << 30)
 
struct edge{
 
  int cost, to;
 
};
 
struct state{
 
  int node, cost;
  bool operator <(const state &b)const{
    return cost > b.cost;
  }
};
 
int n;
int d[10001];
vector<edge> glaph[10001];
priority_queue<state> qu;
 
void sss(){
 
  fill(d,d+10001,INF);
  qu.push((state){0,0});
  d[0] = 0;
 
  while(!qu.empty()){
 
    state info;
    info = qu.top();
    qu.pop();
 
    for(int i = 0; i < (double)glaph[info.node].size(); i++){
      if(d[glaph[info.node][i].to] > glaph[info.node][i].cost + d[info.node]){
      d[glaph[info.node][i].to] = glaph[info.node][i].cost + d[info.node];
      qu.push((state){glaph[info.node][i].to,d[info.node]}); 
      }
    }
  }
 
  for(int i = 0; i < n; i++){
    cout << i << " " << d[i] << endl;
  }
   
 
 
 
}
 
int main(){
 
  cin >> n;
 
  for(int i = 0; i < n; i++){
    int k, v, c, u;
    cin >> u >> k;
    for(int j = 0; j < k; j++){
      cin >> v >> c;
      glaph[u].push_back((edge){c,v});
    }
  }
 
  sss();
 
 
}

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

using namespace std;

class UnionFind {
private:
  std::vector<int> data;
public:
  UnionFind(const int size):data(size,-1){}
  void union_set(int x, int y){
    x = this->get_root(x);
    y = this->get_root(y);
    
    if (x != y) {
      if (this->data[y] < data[x]) {
        swap(x, y);
      }
      this->data[x] += this->data[y];
      this->data[y] = x;
    }  
  }
  bool is_same(const int x, const int y){
    return this->get_root(x) == this->get_root(y);
  }
  int get_root(const int x){
    return this->data[x] < 0 ? x : this->data[x] = this->get_root(this->data[x]);
  }
  int get_size(int x){
    return -this->data[this->get_root(x)];
  }
};

using Edge = struct edge{
  int from, to, cost;
  edge(const int s, const int t, const int c):from(s),to(t),cost(c){}
  bool operator<(const edge& e) const {return cost < e.cost;}
};

struct Graph{
  int v_size;
  vector<Edge> edge_set;
  
  Graph(const int v_size):v_size(v_size){}
  
  void add_edge(const int s, const int t, const int w){
    this->edge_set.emplace_back(Edge{s, t, w});
  }
};

int mst(Graph& g){
  UnionFind uf(g.v_size);
  int ans {0};

  sort(begin(g.edge_set), end(g.edge_set));

  for(auto&& e : g.edge_set){
    if(!uf.is_same(e.from, e.to)){
      ans += e.cost;
      uf.union_set(e.from, e.to);
    }
  }
  
  return ans;
}

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

  int x;
  for(int i = 0; i < n; ++i){
    for(int j = 0; j < n; ++j){
      cin >> x;
      if(x != -1){
        g.add_edge(i, j, x);
      }
    }
  }

  cout << mst(g) << endl;
}

C++: #include <iostream>
#include <sstream>
#include <cstdio>
#include <stdlib.h>
#include <string>
#include <vector>
#include <algorithm>
using namespace std;
#define max 2001
#define INF 200000000
int color[max],p[max],n;
int m[max][max],d[max];
void prim(){
  int mincost,u,i;
  p[0]=-1;
  for(i=1;i<n;i++)d[i]=INF;
  while(1){
    mincost = INF;
    for(i=0;i<n;i++){
      if(color[i]!=1&&d[i]<mincost){
	mincost=d[i];
	u=i;
      }
    }
    if(mincost==INF)break;
    color[u]=1;
    for(int j=0;j<n;j++){
      if(color[j]!=1&&m[u][j]!=-1)
	if(m[u][j]<d[j]){
	  d[j]=m[u][j];
	  p[j]=u;
	  color[j]=-1;
	}
    }
  }
}
int main(){
  int sum=0;
  cin>>n;
  for(int i=0;i<n;i++)
    for(int j=0;j<n;j++)
      cin>>m[i][j];
  prim();
  for(int i=0;i<n;i++)
    sum+=d[i];

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

C++: #define _CRT_SECURE_NO_WARNINGS
#define _USE_MATH_DEFINES
//#include "MyMath.h"
//#include "MyDisjointset.h"
#include <iostream>
#include <vector>
#include <algorithm>
#include <queue>
#include <functional>
#include <stdio.h>
using namespace std;
typedef pair<int, int> P;
const int INF = 2000000000;
int main() {
	int n; cin >> n;
	int m[101][101];
	for (int i = 0; i < n; i++)for (int j = 0; j < n; j++)
		cin >> m[i][j];
	int res = 0;
	int *d = new int[n];
	fill(d, d + n, INF); 
	d[0] = 0;
	bool *visit = new bool [n];
	priority_queue <P, vector<P>, greater<P> > q;
	q.push(P(d[0], 0));
	while (!q.empty()) {
		int f = q.top().first, s = q.top().second;
		visit[s] = true;
		res += f;
		q.pop();
		for (int i = 0; i < n; i++)
			if (!visit[i] && m[s][i] != -1 && m[s][i] > d[i]) {
				m[s][i] = d[i];
				q.push(P(d[i], i));
			}
	}
	cout << res << endl;
	delete[] d, visit;
	return 0;
}