Go: package main

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

const (
	WHITE int = iota
	GRAY
	BLACK
)

type graph struct {
	G [][]int
	C []int
	D []int
	P []int
}

var INFTY = 1 << 32

func constructGraph() *graph {
	sc := bufio.NewScanner(os.Stdin)
	sc.Scan()
	n, _ := strconv.Atoi(sc.Text())

	g := make([][]int, n)
	c := make([]int, n)
	d := make([]int, n)
	p := make([]int, n)

	for i := 0; i < n; i++ {
		sc.Scan()
		fields := strings.Fields(sc.Text())
		g[i] = toIntSlice(fields)
	}

	return &graph{g, c, d, p}
}

func (g *graph) initMst() {
	for i := 0; i < len(g.G); i++ {
		g.C[i] = WHITE
		g.D[i] = INFTY
	}
	g.D[0] = 0
	g.P[0] = -1
}

func (g *graph) primMst() int {
	g.initMst()

	var u int
	for {
		mincost := INFTY
		for i := 0; i < len(g.G); i++ {
			if g.C[i] != BLACK && g.D[i] < mincost {
				mincost = g.D[i]
				u = i
			}
		}

		if mincost == INFTY {
			break
		}

		g.C[u] = BLACK

		for i := 0; i < len(g.G); i++ {
			if g.C[i] != BLACK && g.existEdge(u, i) {
				if g.G[u][i] < g.D[i] {
					g.D[i] = g.G[u][i]
					g.P[i] = u
				}
			}
		}
	}

	totalCost := 0
	for _, cost := range g.D {
		totalCost += cost
	}
	return totalCost
}

func (g *graph) existEdge(u, v int) bool {
	return g.G[u][v] != INFTY && g.G[v][u] != INFTY
}

func toIntSlice(s []string) []int {
	a := make([]int, len(s))
	for i, v := range s {
		num, _ := strconv.Atoi(v)
		if num == -1 {
			num = INFTY
		}
		a[i] = num
	}
	return a
}

func main() {
	g := constructGraph()
	fmt.Println(g.primMst())
}

C++: #include <iostream>
#include <utility>
#include <algorithm>
#define MAX 150
#define rep(i,p) for(int i=0;i<p;i++)
#define rep1(i,p) for(int i=1;i<=p;i++)
using namespace std;
int n,temp,a,b,size,ra,rb;
int A[MAX];
int B[MAX];
int W[MAX];
int V[MAX];
pair<int,int> edge[MAX];
int root (int child) {
  int a = child;
  while (V[a] != a) {
    a = V[a];
  }
  return a;
}
int main(){
  size = 0;
  cin >> n;
  rep(i,n) {
    rep(j,n) {
      cin >> W[size];
      if (i <= j && W[size] != -1) { 
        // cout <<  A[size] << " " << B[size] << " " << j << endl;        
        A[size] = i;
        B[size] = j;        
        edge[size].first = W[size];
        edge[size].second = size;
        size++;
      }
    }
  }
  // cout << endl;
  // rep(i,size) {
  //   cout << A[edge[i].second] << " " << B[edge[i].second]
  //        << " " << edge[i].first << endl;;
  // }
  // sort by lenght of edge
  sort(edge, edge+size+1);
  
  int sum = 0;
  rep(i,n) V[i] = i;
  rep(i,size) {
    // if (edge[i].first == -1) continue;
    temp = edge[i].second;
    // a , b : vertex
    a = A[temp];
    b = B[temp];
    ra = root(a);
    rb = root(b);
    if (ra != rb) {
      // ?????????????????????
      sum += edge[i].first;
      V[ra] = rb;
      // if (ra != a && rb == b){     
      //   V[b] = ra;
      // } else if (ra == a && rb != b) {
      //   V[a] = rb;
      // } else if (ra == a && rb == b) {        
      //   V[a] = b;
      // } else if (ra != a && rb != b) {                
      //   V[ra] = rb;
      // }
    }
  }
  cout << sum+1 << endl;
  return 0;
}

C++: #include <iostream>
using namespace std;
const int MAXn=100;
const int INFTY=1<<21;

int n,M[MAXn][MAXn],col[MAXn],d[MAXn],p[MAXn];

void prim()
{
	for(int i=0;i<n;i++)
	{
		col[i]=0;
		d[i]=INFTY;
	}
	d[0]=0;
	p[0]=-1;
	
	while(1)
	{
		int mincost=INFTY;
		int u;
		for(int i=0;i<n;i++)
		{
			if(col[i]!=2&&d[i]<mincost)
			{
				mincost=d[i];
				u=i;
			}
		}
		if(mincost==INFTY)break;
		col[u]=2;
		for(int v=0;v<n;v++)
		{
			if(col[v]!=2&&M[u][v]!=INFTY)
			{
				if(M[u][v]<d[v])
				{
					d[v]=M[u][v];
					p[v]=u;
					col[v]=1;
				}
			}
		}
	}
	return;
}

int sum()
{
	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++)
	{
		cin>>M[i][j];
		if(M[i][j]==-1)M[i][j]=INFTY;
	}
	prim();cout<<sum()<<endl;
	return 0;
}

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

int V, E, d[105][105], INF = 1e9;

int Prim() {
    int s = 0, c[105], n[105], ans = 0;
    set<int> U;
    for (int i = 1; i < V; i++) U.insert(i);
    bool p[10] = {};

    for (int i = 0; i < V; i++) {
        c[i] = d[s][i];
        n[i] = s;
    }
    vector<pair<int, int>> T;
    while (!U.empty()) {
        int mn = INF, w = -1;
        for (auto& i : U) {
            if (c[i] < mn) {
                mn = c[i];
                w = i;
            }
        }
        U.erase(w);
        T.emplace_back(w, n[w]);
        ans += d[w][n[w]];
        for (auto& i : U) {
            if (d[w][i] < c[i]) {
                c[i] = d[w][i];
                n[i] = w;
            }
        }
    }
    return ans;
}

int main() {
    cin >> V;
    for (int i = 0; i < V; i++) {
        for (int j = 0; j < V; j++) {
            cin >> d[i][j];
            if (d[i][j] == -1) d[i][j] = INF;
        }
    }

    cout << Prim() << endl;
}

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

#define MAX_NUM 10000

using namespace std;

int main(){
	priority_queue<int, vector<int>, less<int> >heap;
	int L,P,N,A[MAX_NUM],B[MAX_NUM],num=0;
	cin>>N>>L>>P;
	for(int i=0;i<N;i++){
		cin>>A[i];
	}
	for(int i=0;i<N;i++){
		cin>>B[i];
	}
	int i=0;
	while(L>P){
		while(A[i]<=P && i<N){
			heap.push(B[i]);
			i++;
		}
		if(heap.empty()==1){
			cout<<-1<<endl;
		}
		P+=heap.top();
		heap.pop();
		num++;
	}
	cout<<num<<endl;
	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 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=-1;
    for(int i=0;i<n;i++){
      if(minv>d[i] && color[i] !=BLACK){
        u=i;
        minv=d[i];
      }
    }
    if(u==-1)break;
    color[u]=BLACK;
    for(int v=0;v<n;v++){
      if(color != 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;
}

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

#define MAX_N 100
#define MAX_EDGE_COST 20000
int Graph[MAX_N+1][MAX_N+1];
int n;

int prim(int initial_vertex) {
  bool visited[n+1];
  for(int i=1;i<=n;i++) visited[i] = false;
  vector<int> vertexes;
  vertexes.push_back(initial_vertex);
  visited[initial_vertex] = true;
  int total_edge_cost = 0;
  while(vertexes.size() <= n) {
    // find minimum edge cost in vertexes
    int minimum_edge_cost = MAX_EDGE_COST;
    int next_v;
    for(int i=0;i<vertexes.size();i++) {
      int v = vertexes[i];
      for(int j=1;j<=n;j++) {
        if(!visited[j]) {
          if(Graph[v][j] != -1) {
            if(Graph[v][j] < minimum_edge_cost) {
              minimum_edge_cost = Graph[v][j];
              next_v = j;
            }
          }
        }
      }
    }
    vertexes.push_back(next_v);
    total_edge_cost += minimum_edge_cost;
  }
  return total_edge_cost;
}

int main() {
  scanf("%d",&n);
  for(int i=1;i<=n;i++) {
    for(int j=1;j<=n;j++) {
      scanf("%d ",&Graph[i][j]);
    }
  }
  printf("%d\n",prim(1));
}