Go: package main

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

const BIG_COST = 3000

const (
	ST_NOT_YET = iota
	ST_JOINED
)

func main() {
	sc := bufio.NewScanner(os.Stdin)
	sc.Split(bufio.ScanWords)

	nNodes := scanInt(sc)
	costs := make([][]int, nNodes)

	for r := 0; r < nNodes; r++ {
		costs[r] = make([]int, nNodes)
		for c := 0; c < nNodes; c++ {
			costs[r][c] = scanInt(sc)
		}
	}

	states := make([]int, nNodes)
	minCosts := make([]int, nNodes)

	for i := 1; i < nNodes; i++ {
		minCosts[i] = BIG_COST
	}

	for {
		var u int
		minCost := BIG_COST

		for i := 0; i < nNodes; i++ {
			if states[i] != ST_JOINED && minCosts[i] < minCost {
				minCost = minCosts[i]
				u = i
			}
		}

		// 全てのノードが MST に JOIN できたので終了。
		if minCost == BIG_COST {
			break
		}

		states[u] = ST_JOINED

		for v := 0; v < nNodes; v++ {
			cost := costs[u][v]

			// MST内の u と MST外の v との辺の重みをそれぞれ minCosts[v] として
			// 保存しておく。このうち辺の重みが最小となる v が次のループで MST に JOIN する。
			if states[v] != ST_JOINED && cost != -1 && cost < minCosts[v] {
				minCosts[v] = cost
			}
		}
	}

	sum := 0
	for _, cost := range minCosts {
		sum += cost
	}
	fmt.Println(sum)
}

func scanInt(sc *bufio.Scanner) int {
	sc.Scan()
	v, _ := strconv.Atoi(sc.Text())
	return v
}

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

static const int MAX = 10000;
static const int INFTY = (1<<21);
static const int WHITE = 0;
static const int GRAY = 1;
static const int BLACK = 2;

int n;
vector<pair<int,int> > adj[MAX];

void dijkstra(){
    priority_queue<pair<int,int> > PQ;
    int color[MAX];
    int d[MAX];
    for(int i=0; i<n; i++){
        d[i] = INFTY;
        color[i] = WHITE;
    }
    
    d[0] = 0;
    PQ.push(make_pair(0,0));
    color[0] = GRAY;
    
    while(!PQ.empty()){
        pair<int,int> f = PQ.top(); PQ.pop();
        int u = f.second;
        color[u] = BLACK;
        
        if(d[u] < f.first*(-1)) continue;
        
        for(int j=0; j<adj[u].size(); j++){
            int v = adj[u][j].first;
            if(color[v]==BLACK) continue;
            if(d[v]>d[u]+adj[u][j].second){
                d[v] = d[u]+adj[u][j].second;
                PQ.push(make_pair(d[v]*(-1),v));
                color[v] = GRAY;
            }
        }
    }
    
    for(int i=0; i<n; i++){
        cout << i << " " << (d[i]==INFTY ? -1 : d[i]) << endl;
    }
}

int main(){
    int k,u,v,c;
    
    cin >> n;
    for(int i=0; i<n; i++){
        cin >> u >> k;
        for(int j=0; j<k; j++){
            cin >> v >> c;
            adj[u].push_back(make_pair(v,c));
        }
    }
    
    dijkstra();
    
    return 0;
}

C++: #include<iostream>

using namespace std;

int main()
{
    int n, A[100][100], B[100] = { 0 };
    int min;
    cin >> n;
    for (int i = 0; i < n; i++) {
        for (int j = 0; j < n; j++) {
            cin >> A[i][j];
            if(A[i][j]!='-1')
            B[i] += A[i][j];
        }
    }
    min = B[0];
    for (int i = 1; i < n; i++) {
        if (min > B[i])min = B[i];
    }
    cout << min << endl;
    return 0;
}

C++: #include <iostream>
#include <string>
#include <vector>
#include <algorithm>
#include <cmath>
#include <cassert>
#define FOR(i,a,b) for(int i=(a);i<(b);i++)
#define REP(i,n) FOR(i,0,n)
#define rep(i,n) FOR(i,0,n)
#define DEBUG(x) cout<<#x<<": "<<x<<endl
#define vint vector<int>
#define vdouble vector<double>
#define vstring vector<string>
using namespace std;
#include <functional>

#include<map>
#include<set>
#include<queue>

typedef long long ll;
typedef unsigned long long ull;

const int MAX_N = 100;

int N;

class Edge{
public:
	int from, to, cost;
	Edge(int from = 0, int to = 0, int cost = 0) :
		from(from), to(to), cost(cost){}
	
	bool operator < (const Edge &e) const{
		return cost < e.cost;
	}
	bool operator > (const Edge &e) const{
		return cost > e.cost;
	}

};

class Node{
public:
	vector<Edge> edges;
	int color;
	Node(){
		color = 0;
	}
};

class Graph{
public:
	vector<Node> nodes;
	Graph(int n) {
		rep(i, n) { Node n;  nodes.push_back(n); }
	}
};

int main() {

	cin >> N;
	Graph g(N);

	rep(i, N)
	   rep(j, N){
		int cost; cin >> cost;
		if (cost != -1){
			Edge e(i, j, cost);
			g.nodes[i].edges.push_back(e);
		}
	}

	rep(i, N) { g.nodes[i].color = 0; }

	int i = 0;
	g.nodes[i].color = 1;

	priority_queue<Edge, vector<Edge>, greater<Edge> > pq;
	for (auto e : g.nodes[i].edges){
		pq.push(e);
	}

	int ret = 0;
	while (!pq.empty()){
		Edge e = pq.top(); pq.pop();
		Node *n = &g.nodes[e.to];
		if (n->color != 0){ continue; }
		
		n->color = 1;
		ret += e.cost;

		for (auto e : n->edges){
			pq.push(e);
		}
	}

	cout << ret << endl;
}

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

const int MAX = numeric_limits<int>::max();

class Node{
public:
  int _id;
  bool _isFound;
  vector<int> _adj_index; // 隣接点のid
  vector<int> _adj_vertices;  // 隣接点との距離(重み)

  void init(int id, int n){
    _id = id;
    _isFound = false;
    for(auto i = 0; i < n; i++){
      _adj_vertices.push_back(MAX);
    }
  }
};

void inputGraph(vector<Node>& graph){
  for(auto i = 0; i < graph.size(); i++){
    graph[i].init(i, graph.size());
    for(auto j = 0; j < graph.size(); j++){
      int tmp;
      cin >> tmp;
      if(tmp != -1){
        graph[i]._adj_index.push_back(j);
        graph[i]._adj_vertices[j] = tmp;
      }
    }
  }
}

int mst(vector<Node>& graph, int search){
  auto sum = 0;
  vector<int> searched; // 木に追加済みのNodeのid
  searched.push_back(search);
  graph[searched[0]]._isFound = true;
  int minNodeIndex;

  while(searched.size() < graph.size()){
    auto compare = MAX;

    for(auto i = 0; i < searched.size(); i++){
      for(auto j = 0; j < graph[searched[i]]._adj_index.size(); j++){
//  cout << "call in for " << j << endl;
//  cout << compare << endl;
        Node searching = graph[searched[i]];
        if(!graph[searching._adj_index[j]]._isFound &&
           searching._adj_vertices[searching._adj_index[j]] < compare){
          // 木の隣接点で最短
          compare = searching._adj_vertices[searching._adj_index[j]];
          minNodeIndex = searching._adj_index[j];
 //         cout << "added" << endl;
        }
      }
    }
    if(compare != MAX){
      sum += compare;
      graph[minNodeIndex]._isFound = true;
      searched.push_back(minNodeIndex);
//      cout << endl << "minNodeIndex:" << minNodeIndex << endl;
    }

  }
  return sum;
}

int main(){
  int n;
  cin >> n;
  vector<Node> graph(n);

  inputGraph(graph);
  cout << mst(graph, 0) << endl;

  return 0;
}

C++: #include <bits/stdc++.h>

using namespace std;

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

    int adj[n][n];
    int inf = 2001;

    for(int i = 0; i < n; i++) {
        for(int j = 0; j < n; j++) {
            int k; cin >> k;
            adj[i][j] = k == -1 ? inf : k;
        }
    }

    int sd[n] = {1};
    int ans = 0;

    while(true) {
        int a = -1, c = inf;

        for(int i = 0; i < n; i++) {
            if(sd[i] == 0) { 
                if(a == -1) {
                    a = i;
                }
                continue;
            }
            for(int j = 0; j < n; j++) {
                if(adj[i][j] < c && sd[j] == 0) {
                    c = adj[i][j];
                    a = j;
                }
            }
        }

        if(a == -1) break;

        ans += c;
        sd[a] = 1;
    }

    cout << ans << endl;

}