Go: package main

import (
	"bufio"
	"container/heap"
	"fmt"
	"os"
	"strconv"
)

type Node struct {
	id     int
	weight int
}

func init() {
	sc.Split(bufio.ScanWords)
}

type NodeHeap []Node

func (h NodeHeap) Len() int           { return len(h) }
func (h NodeHeap) Less(i, j int) bool { return h[i].weight < h[j].weight }
func (h NodeHeap) Swap(i, j int)      { h[i], h[j] = h[j], h[i] }

func (h *NodeHeap) Push(x interface{}) {
	*h = append(*h, x.(Node))
}

func (h *NodeHeap) Pop() interface{} {
	old := *h
	n := len(old)
	x := old[n-1]
	*h = old[0 : n-1]
	return x
}

var sc = bufio.NewScanner(os.Stdin)

func scanInt() int {
	num, _ := strconv.Atoi(scanString())
	return num
}

func scanString() string {
	sc.Scan()
	return sc.Text()
}

func init() {
	sc.Split(bufio.ScanWords)
}

func main() {
	n := scanInt()

	list := make([][]int, n)
	seen := make([]bool, n)
	for i := range list {
		list[i] = make([]int, n)
		for j := range list[i] {
			list[i][j] = scanInt()
		}
	}

	start := Node{id: 0, weight: 0}
	h := &NodeHeap{start}
	heap.Init(h)

	sum := 0
	for h.Len() > 0 {
		node := heap.Pop(h).(Node)
		if seen[node.id] {
			continue
		}
		seen[node.id] = true
		sum += node.weight

		for i, w := range list[node.id] {
			if w < 0 {
				continue
			}
			heap.Push(h, Node{id: i, weight: w})
		}
	}

	fmt.Println(sum)
}

C++: #include<iostream>
#include<vector>
#include<queue>
using namespace std;
enum COLOR{WHITE, BLACK};

struct Edge{
    int w, i, j;
    Edge(int w_, int i_, int j_) : w(w_), i(i_), j(j_) {}
    bool operator< (const Edge& right) const{
        return w > right.w;
    }
};

int main(){
    int n;
    cin >> n;
    vector<vector<int> > G(n, vector<int>(n));
    for (int i = 0; i < n; i++) {
        for (int j = 0; j < n; j++) {
            cin >> G[i][j];
            if (G[i][j] == -1) G[i][j] = 1e8;
        }
    }
    vector<COLOR> state(n, WHITE);
    priority_queue<Edge> prim;
    state[0] = BLACK;
    int sum = 0;
    int idx_new_gray = 0;
    for (int i = 1; i < n; i++) {
        for (int j = 0; j < n; j++) {
            if (state[j] != WHITE) continue;
            prim.push(Edge(G[idx_new_gray][j], idx_new_gray, j));
        }
        while (state[prim.top().j] == BLACK) prim.pop();
        sum += G[prim.top().i][prim.top().j];
        state[prim.top().j] = BLACK;
        idx_new_gray = prim.top().j;
        prim.pop();
    }
    cout << sum << 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;

    // 黒以外のやつから最小を探す
    for(int i=0;i<n;i++)
    {
      if(minv>d[i] && color[i] != BLACK)
      {
        u=i;
        minv=d[i];
      }
    }

    // 全部黒だったらループ終了
    if(u==-1)break;

    color[u] = BLACK;

    // u番目とつながるものに値を与える(黒以外)
    for(int v=0;v<n;v++)
    {
      if(color[v] != 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;
  return 0;
}

C++: #include<cstdio>
#include<vector>
#define N_MAX 105
#define INF 32700
using namespace std;
short adj[N_MAX][N_MAX];
struct Node{
    char parent;//父节点
    short weight;//权值
    bool state;//节点状态
}nodes[N_MAX];
char n;
int solve() {
    int res = 0;
    nodes[0].weight = 0;
    nodes[0].parent = -1;
    nodes[0].state = true;
    char nowParent = 0;
    while(true) {
        for(char j = 0; j < n; j++) {
            if(nodes[j].weight > adj[nowParent][j]&&!nodes[j].state) {
                nodes[j].weight = adj[nowParent][j];
            }
        }
        char minId = n;
        for(char i = 0; i < n; i++) {
            if(!nodes[i].state) {
                if(nodes[i].weight < nodes[minId].weight) {
                    minId = i;
                }
            }
        }
        if(minId == n) break;
        else nodes[minId].state = true;
        nodes[minId].parent=nowParent;
        nowParent=minId;
    }
    for(char i = 0; i < n; i++) {
        res += nodes[i].weight;
    }
    return res;
}

int main(){
    freopen("D:/works/C++200/try132_AOJ_ALDS1_12_A/data.txt", "r", stdin);
    scanf("%d", &n);
    for(char i=0;i<n;i++){
        for(char j=0;j<n;j++){
            scanf("%d", &adj[i][j]);
            if(adj[i][j]==-1) adj[i][j]=INF;
        }
        nodes[i].weight=INF;//初始权值
    }
    nodes[n].weight=INF;
    printf("%d\n", solve());
    return 0;
}

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

#define INF (1<<29)

int G[100][100], n;

int prim(){
  int p[100], d[100], c[100];
  int u;

  for(int i = 0; i < n; i++){
    d[i] = INF;
    p[i] = -1;
    c[i] = 0;
  }

  d[0] = 0;

  while(1){
    int minv = INF;
    u = -1;
    for(int i = 0; i < n; i++){
      if(minv > d[i] && c[i] != 2){
        u = i;
        // cout << u << endl;
        minv = d[i];
      }
    }

    if(u == -1) break;
    c[u] = 2;
    for(int v = 0; v < n; v++){
      if(c[v] != 2 && G[u][v] != INF){
        if(d[v] > G[u][v]){
          d[v] = G[u][v];
          p[v] = u;
          c[v] = 1;
        }
      }
    }
  }

  int sum = 0;
  for(int i = 0; i < n; i++){
    if(p[i] != -1) sum+=G[i][p[i]];
    // cout << p[i] << endl;
  }
  return sum;
}


  int main(){

    cin >> n;
    for(int i = 0; i < n; i++){
      for(int j = 0; j < n; j++){
        int v;
        cin >> v;
        G[i][j] = v;
        if(v == -1) G[i][j] = INF;
      }
      // cout << endl;
    }

    cout << prim() << endl;

  }

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

using namespace std;

using pii = pair<int, int>;

struct Graph{
  int v_size;
  vector<vector<pii>> adj;
  
  Graph(const int v_size):v_size(v_size){
    this->adj.resize(v_size);
  }
  
  void add_edge(const int s, const int t, const int w){
    this->adj[s].emplace_back(pii(t, w));
  }
};

int mst(const Graph& g){
  constexpr int INF{INT_MAX};
  
  vector<int> d(g.v_size, INF);
  priority_queue<pii, vector<pii>, greater<pii>> pq;

  d[0] = 0;
  pq.push(pii(0, 0));

  int ans {0};
  
  while(!pq.empty()){
    auto cost {pq.top().first};
    auto v {pq.top().second};
    pq.pop();

    if(d[v] < cost) continue;

    ans += cost;
    d[v] = -INF;

    for(int i = 0; i < g.adj[v].size(); ++i){
      auto to {g.adj[v][i].first};
      auto next_cost {g.adj[v][i].second};

      if(d[to] > next_cost){
        d[to] = next_cost;
        pq.push(pii(next_cost, 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;
}