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 <cstdio>
#include <algorithm>
#include <cmath>
#include <climits>
#include <string>
#include <vector>
#include <utility>
#include <functional>
#include <stack>
#include <queue>
#include <map>
#include <set>
#include <cassert>

using namespace std;

typedef long long ll;
typedef pair<int, int> P;

const ll MOD = ll(1e9) + 7;
const ll INF = LLONG_MAX;
const ll MAX_N = ll(1e5) + 5;
const double EPS = 10e-8;
const double PI = 3.14159265359;

#define REP(i, n) for (ll i = 0; i < n; i++)
#define REPR(i, n) for (ll i = n; i >= 0; i--)
#define FOR(i, m, n) for (ll i = m; i < n; i++)

int dx[] = {1, 0, -1, 0}, dy[] = {0, 1, 0, -1};

struct UF{
    static const int MAX_N = 100000;
    int p[MAX_N];
    int r[MAX_N];

    void init(int n){
        REP(i,n){
            p[i]=i;
            r[i]=0;
        }
    }
    int find(int x){
        if(p[x]==x)return x;
        return p[x] = find(p[x]);
    }
    void unite(int x, int y){
        x = find(x);
        y = find(y);
        if(x == y)return;
        if(r[x] < r[y])swap(x,y);
        if(r[x]==r[y])r[x]++;
        p[y]=x;
    }
    bool same(int x, int y){
        return find(x)==find(y);
    }
};

int n;
vector<pair<int,P>> es;

int MST(){
    int res = 0;
    sort(es.begin(), es.end());
    UF g;
    g.init(n);
    REP(i,es.size()){
        int cost = es[i].first, u = es[i].second.first, v = es[i].second.second;
        if(g.same(u,v))continue;
        g.unite(u,v);
        res += cost;
    }
    return res;
}

int main() {
    cin >> n;
    REP(i,n){
        REP(j,n){
            int a;
            cin >> a;
            if(a==-1)continue;
            es.push_back({a,{i,j}});
        }
    }
    cout << MST() << endl;
    return 0;
}

C++: #include<iostream>
#include<cstring>
#include<algorithm>
using namespace std;

int x[10000][10000];
int MIN[10000];
int MINX = 0;
int MINZ = 0;

int main() {
	memset(MIN, 127, sizeof(MIN));
	int n, a;
	cin >> n;
	for (int i = 0; i < n; i++) {
		for (int j = 0; j < n; j++) {
			cin >> a;
			x[i][j] = a;
		}
	}
	for(int h=0;h<n;h++){
		memset(MIN, 127, sizeof(MIN));
		MINX=0;
		MIN[h] = 0;
		for (int i = 0; i < n; i++) {
			for (int j = 0; j < n; j++) {
				for (int k = 0; k < n; k++) {
					if (x[j][k] != -1) {
						MIN[k] = min(MIN[k], x[j][k]);
					}
				}
			}
		}
		for (int i = 0; i < n; i++) {
			MINX += MIN[i];
		}
		MINZ=min(MINZ,MINX);
	}
	cout << MINZ << 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 (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 <bits/stdc++.h>
using namespace std;
#define REP(i,n) for(int i=0; i<(n); i++)
#define ALL(n) begin(n),end(n)
using Graph=vector<vector<int>>;

int n;
// プリムのアルゴリズム
vector<int> included;
int Prim(const Graph &G,int v,int &cost){
    // 頂点vは木に含まれた
    included.push_back(v);
    // n頂点全てが木に含まれていれば終了
    if(included.size()==n) return cost;

    int min_=2001;
    int to=-1;
    for(int x:included){
        for(int y=0; y<n; y++){
            if(G[x][y]<min_ && G[x][y]!=-1){
                // yがincludedに含まれている場合，何もしない
                if(find(included.begin(),included.end(),y)!=included.end()){
                    continue;
                }
                min_=G[x][y];
                to=y;
            }
        }
    }

    // 頂点toを追加して，Primを呼び出す
    cost+=min_;
    return Prim(G,to,cost);
}

int main(){
    cin>>n;
    
    // 隣接行列を受け取る
    Graph G(n,vector<int>(n));
    REP(i,n){
        REP(j,n){
            cin>>G[i][j];
        }
    }

    int cost=0;

    cout<<Prim(G,0,cost)<<endl;
}

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[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;
    
}