Go: package main

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

const (
	MAX_N      = 200
	MAX_WEIGHT = 2000
)

type Edge struct {
	start  int
	end    int
	weight int
}

type ShortestInfo struct {
	edges    []Edge
	shortest int
}

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

	n, err := nextInt(sc)
	if err != nil {
		panic(err)
	}

	shortestList := make([]ShortestInfo, n)
	for i := 1; i < n; i++ {
		shortestList[i] = ShortestInfo{edges: []Edge{}, shortest: MAX_N*MAX_WEIGHT + 1}
	}

	adjacentMatrix := make([][]int, n)
	for i := 0; i < n; i++ {
		adjacentMatrix[i] = make([]int, n)
		for j := 0; j < n; j++ {
			v, err := nextInt(sc)
			if err != nil {
				panic(err)
			}
			adjacentMatrix[i][j] = v
		}
	}

	mst([]int{1}, shortestList, adjacentMatrix)
	fmt.Println(calculateMinWeight(shortestList))
}

func calculateMinWeight(shortestList []ShortestInfo) int {
	visitedList := make([]bool, len(shortestList))
	visitedList[0] = true
	sumWeight := 0
	for !visitedAll(visitedList) {
		shortestInfo := shortestList[0]
		shortestList = shortestList[1:]
		edges := shortestInfo.edges
		for _, edge := range edges {
			if !visitedList[edge.end-1] {
				visitedList[edge.end-1] = true
				sumWeight += edge.weight
			}
		}
	}
	return sumWeight
}

func visitedAll(visitedList []bool) bool {
	for _, v := range visitedList {
		if !v {
			return false
		}
	}
	return true
}

func mst(nodeStack []int, shortestList []ShortestInfo, adjacentMatrix [][]int) {
	for len(nodeStack) > 0 {
		currentNode := nodeStack[0]
		nodeStack = nodeStack[1:]
		currentShortest := getShortest(currentNode, shortestList)
		adjacents := findAdjacents(currentNode, adjacentMatrix)
		for i := 0; i < len(adjacents); i++ {
			adj := adjacents[i]
			s := getShortest(adj.end, shortestList)
			if currentShortest.shortest+adj.weight < s.shortest || (currentShortest.shortest+adj.weight == s.shortest && len(currentShortest.edges)+1 > len(s.edges)) {
				setShortest(adj.end, adj, currentShortest, shortestList)
				nodeStack = append(nodeStack, adj.end)
			}
		}
	}
}

func getShortest(node int, shortestList []ShortestInfo) ShortestInfo {
	return shortestList[node-1]
}

func setShortest(node int, edge Edge, currentShortest ShortestInfo, shortestList []ShortestInfo) {
	newEdges := make([]Edge, len(currentShortest.edges)+1)
	for i := 0; i < len(newEdges)-1; i++ {
		newEdges[i] = currentShortest.edges[i]
	}
	newEdges[len(newEdges)-1] = edge
	shortestInfo := ShortestInfo{edges: newEdges, shortest: currentShortest.shortest + edge.weight}
	shortestList[node-1] = shortestInfo
}

func findAdjacents(currentNode int, adjacentMatrix [][]int) []Edge {
	adjacents := adjacentMatrix[currentNode-1]
	edges := []Edge{}
	for i, v := range adjacents {
		if v > 0 {
			edges = append(edges, Edge{start: currentNode, end: i + 1, weight: v})
		}
	}
	return edges
}

func nextInt(sc *bufio.Scanner) (int, error) {
	sc.Scan()
	return strconv.Atoi(sc.Text())
}

C++: #include <stdio.h>
#include <iostream>
#include <utility>
#include <algorithm>
#include <math.h>
#include <vector>
using namespace std;

class edge
{
  public:
    int i, j, weigt;
    bool operator()(edge e1, edge e2)
    {
        return e1.weigt < e2.weigt;
    }
};
edge e[10000];
int main()
{
    int n;
    cin >> n;
    int b[n][n] = {};
    int k = 0;
    int tmp = 0;
    int sum = 0;
    for (int i = 0; i < n; i++)
    {
        for (int j = 0; j < n; j++)
        {
            cin >> tmp;
            if (j < i + 1 || tmp < 0)
                continue;
            e[k].i = i;
            e[k].j = j;
            e[k].weigt = tmp;
            k++;
        }
    }
    sort(e, e + k, edge());
    for (int i = 0; i < k; i++)
    {
        if (b[e[i].i][e[i].j] == 0)
        {
            cout << e[i].weigt << "\n";
            sum += e[i].weigt;
            b[e[i].i][e[i].j] = 1;
            b[e[i].j][e[i].i] = 1;
            for (int j = 0; j < n; j++)
            {
                if (b[e[i].i][j] == 1 || b[e[i].j][j] == 1)
                    b[e[i].i][j] = b[e[i].j][j] = b[j][e[i].i] = b[j][e[i].j] = 1;
            }
        }
    }
    cout << sum << "\n";
    return 0;
}

C++: #include <iostream>
#include <limits.h>
using namespace std;

int main(void)
{
	int n, now = 0, flag[101];
	long ans = 0, an[100][100], min[100];

	cin >> n;

	for(int i = 0; i < n; i++) {
		for(int j = 0; j < n; j++) {
			cin >> an[i][j];
		}
		min[i] = LONG_MAX - 1;
		flag[i] = 0;
	}

	do {
		flag[now] = 1;
		flag[100] = 0;

		for(int j = 0; j < n; j++) {
			if(an[now][j] != -1 && an[now][j] < min[j] && flag[j] == 0) {
				min[j] = an[now][j];
			}
		}

		int key = LONG_MAX - 1, key_j;

		for(int j = 0; j < n; j++) {
			if(flag[j] == 0 && min[j] < key) {
				key = min[j];
				key_j = j;
			}
		}

		now = key_j;
		ans += key;

		for(int i = 0; i < n; i++) {
			if(flag[i] == 1) {
				flag[100]++;
			}
		}
	
	}while(flag[100] != n - 1);

	cout << ans << endl;

	return 0;
}

C++: #include <utility>
#include <string>
#include <vector>
#include <algorithm>
#include <iostream>
using namespace std;

int n;					//えぬ
int a[100][100] = {0};	//辺の重さ
int f[100] = {0};		//その頂点がすでに連結済みかどうか、その集団の番号
int c = 0;				//全体の重さ
int d = 1;				//次につける集団番号
int s = 0;				//選んだ本数
vector<int> w;			//木のリスト、軽いもの順
int wc = 0;				//見てる木のリストの位置

int main(){
	cin >> n;
	//まず辺の重さをaに入れる
	//wに辺のリストを入れる
	for ( int i = 0; i < n; i++ ) {
		for ( int j = 0; j < n; j++ ) {
			cin >> a[i][j];
			if ( a[i][j] != -1 && i < j ) w.push_back( a[i][j] );
		}
	}
	sort( w.begin(),w.end() );
	while(true) {									//n-1本選ぶまで無限ループ
		for ( int i = 0; i < n - 1; i++ ) {			// i < j を満たすように木を調べ続ける
			for ( int j = i + 1; j < n; j++ ) {
				if ( a[i][j] != w[wc] ) continue;	//その木が一番軽い木だったらそれを対象に検査を始める
				if ( f[i] > 0 && f[j] > 0 ) {		//その木の両端が両方とも連結済みだったら
					if ( f[i] != f[j] ) {
						int y = f[j];
						for ( int x = 0; x < n; x++ ) {
							if ( f[x] == y ) f[x] = f[i];
						}
						c += a[i][j];
						s++;
					}
				}else if ( f[i] == 0 && f[j] == 0 ) {
					f[i] = d;
					f[j] = d;
					d++;
					c += a[i][j];
					s++;
				}else {
					if ( f[i] == 0 ) {
						f[i] = f[j];
						c += a[i][j];
						s++;
					}else {
						f[j] = f[i];
						c += a[i][j];
						s++;
					}
				}
				wc++;
				a[i][j] = -1;
				if ( s == n-1 ) break;
			}
			if ( s == n-1 ) break;
		}
		if ( s == n-1 ) break;
	}
	cout << c << endl;
	return 0;
}

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

using namespace std;

#define Vi vector<int>
#define FOR(i,s,e) for (int i=s; i<e; i++)
#define ITER(v) v.begin(), v.end()

constexpr int N_MAX = 100;

int weight[N_MAX][N_MAX];

int mst(const int n) {
    bool ismember[n] = {false};
    Vi members;

    members.push_back(0);
    ismember[0] = true;
    int cost = 0;

    FOR(t,1,n) {
        int addcost = -1;
        int newmember = -1;
        for (const int i : members)
        FOR(j,0,n) {
            if (ismember[j]) { continue; }
            const int w = weight[i][j];
            if (w < 0) { continue; }
            if (addcost < 0 || addcost > w) {
                addcost = w;
                newmember = j;
            }
        }
        members.push_back(newmember);
        ismember[newmember] = true;
        cost += addcost;
        //cout << "#" << newmember << endl;
    }
    return cost;
}

int main() {
    cin.tie(0);
    ios::sync_with_stdio(false);

    int n;
    cin >> n;

    FOR(i,0,n) {
        FOR(j,0,n) {
            cin >> weight[i][j];
        }
    }

    int cost = mst(n);
    cout << cost << endl;

    return 0;
}