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 <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;
		flag[i] = 0;
	}

	/* ???????則?????????即?????属????????? */
	do {
		flag[now] = 1;
		flag[100] = 0;
/*
		cout << "\n??? " << now << " ????則???????????????????" << endl;
		cout << "?????贈?????? : ";
		for(int i = 0; i < n; i++) {
			if(flag[i] == 1) {
				cout << i << " ";
			}
		}
		cout << endl;
		cout << "?????即???????属?????????則" << endl;
		for(int i = 0; i < n; i++) {
			if(flag[i] == 0) {
				cout << "??? " << i << " : " << min[i] << endl;
			}
		}
*/
		/* min?????卒??属 */
		for(int j = 0; j < n; j++) {
			if(an[now][j] != -1 && an[now][j] < min[j] && flag[j] == 0) {
/*				cout << "??? " << j <<" ???????属?????????卒??属??????????????? : "<< min[j] << " ??? " << an[now][j] << endl; */
				min[j] = an[now][j];
			}
		}
/*
		cout << "?????即???????属?????????則" << endl;
		for(int i = 0; i < n; i++) {
			if(flag[i] == 0) {
				cout << "??? " << i << " : " << min[i] << endl;
			}
		}
*/
		/* ?測??????蔵?卒蔵???min????属???? */
		long key = LONG_MAX, key_j;

		for(int j = 0; j < n; j++) {
			if(flag[j] == 0 && min[j] < key) {
				key = min[j];
				key_j = j;
			}
		}
/*
		cout << "?則???????????賊??????????????????? : ??? " << key_j << endl;
*/
		/* ?則?????????? */
		now = key_j;
		ans += key;

		/* ??????????????贈????????? */
		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 <iostream>
#include <list>
#include <vector>
#include <map>
#include <set>
#include <queue>
#include <stack>
#include <numeric>
#include <algorithm>
#include <cmath>
#include <string>
using namespace std;
typedef long long lli;
typedef vector<lli> vll;
typedef vector<bool> vbl;
typedef vector<vector<lli> > mat;
typedef vector<vector<bool> > matb;
typedef vector<string> vst;
typedef pair<lli,lli> pll;
typedef pair<double,double> pdd;

vll par;
vll rnk;
void init(lli n){
    par = vll(n);
    rnk = vll(n);
    for(lli i = 0;i < n;i++) par[i] = i;
}
lli find(lli x){
    if(par[x] == x) return x;
    else return par[x] = find(par[x]);
}
void unite(lli x,lli y){
    x = find(x);y = find(y);
    if(x == y) return;
    if(rnk[x] < rnk[y]) par[x] = y;
    else {
        par[y] = x;
        if(rnk[x] == rnk[y]) rnk[x]++;
    }
}
bool same(lli x,lli y){
    return find(x) == find(y);
}

lli n;
vll c,r,l;
vll p;
mat g;
lli ans = 0;

int main(){
    cin >> n;
    g = mat(n,vll(n));
    for(lli i = 0;i < n;i++){
        for(lli j = 0;j < n;j++){
            cin >> g[i][j];
        }
    }
    for(lli i = 0;i < n;i++){
        for(lli j = i+1;j < n;j++){
            if(g[i][j] >= 0) c.push_back(g[i][j]),r.push_back(i),l.push_back(j);
        }
    }
    p = vll(c.size());
    for(lli i = 0;i < p.size();i++) p[i] = i;
    sort(p.begin(),p.end(),[](lli a,lli b){
        return c[a] < c[b];
    });
    init(n);
    for(lli i = 0;i < p.size();i++){
        if(!same(r[p[i]],l[p[i]])) unite(r[p[i]],l[p[i]]),ans += c[p[i]];
    }
    cout << ans << endl;
    return 0;
}

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

using Weight=long long;
struct Edge{
    int from,to;
    Weight weight;
};
bool operator<(const Edge& lhs,const Edge& rhs){
    return lhs.weight<rhs.weight;
}

using Edges=vector<Edge>;
using Graph=vector<Edges>;


Edges MinimumSpanningTree(int n,Edges edges){
    Edges res;
    UnionFind u(n);
    for(int i=0;i<edges.size();i++){
        if(!u.same(edges[i].from,edges[i].to)){
            res.push_back(edges[i]);
            u.unite(edges[i].from,edges[i].to);
        }
    }
    return res;
}

Edges MinimumSpanningTree(const Graph& g){
    Edges edges;
    for(int i=0;i<g.size();i++){
        copy(g[i].begin(),g[i].end(),back_inserter(edges));
    }
    auto res=MinimumSpanningTree(g.size(),edges);
    return res;
}

int main(){
    int n;
    cin>>n;
    Graph g(n);
    for(int i=0;i<n;i++){
        for(int j=0;j<n;j++){
            Weight c;
            cin>>c;
            if(i==j) continue;
            g[i].push_back({i,j,c});
        }
    }
    auto mst=MinimumSpanningTree(g);
    cout<<accumulate(mst.begin(),mst.end(),Weight(0),[](const Weight& lhs,const Edge& rhs){return lhs+rhs.weight;})<<endl;
    return 0;
}