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 <ios>
#include <vector>
#include <queue>
#include <utility>
#include <tuple>

using namespace std;
int Es[100][100] = {{0}};

int MST(int n){
    vector<bool> used(n, false);
    priority_queue< pair<int, int> > pq;
    pq.emplace(0, 0);
    int dist = 0;
    int node = 0;
    int total_dist = 0;
    while (! pq.empty()){
        tie(dist, node) = pq.top();
        pq.pop();
        if (used[node]) continue;
        used[node] = true;
        total_dist -= dist;
        for (int new_node = 0; new_node != n; ++new_node){
            if (used[new_node] || Es[node][new_node] == -1) continue;
            pq.emplace(-Es[node][new_node], new_node);
        }
    }
    return total_dist;
}

int main()
{
    ios::sync_with_stdio(false);
    int n = 0;
    cin >> n;
    for (int i = 0; i != n; ++i){
        for (int j = 0; j != n; ++j){
            cin >> Es[i][j];
        }
    }
    cout << MST(n) << endl;
    return 0;
}

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

#define check cout<<"-------"<<endl
#define debug(x) cout<<x<<endl

#define N 101
#define MAX 2001

int main() {
    cin.tie(0);
    ios::sync_with_stdio(false);
    
    int a[N][N];
    int list[MAX];
    
    int n;
    cin>>n;
    for(int i = 1; i <= n; i++) {
        for(int j = 1; j <= n; j++) {
            cin>>a[i][j];
        }
    }
    
    int sum = 0, min, mini, i, j;
    int lp = n-1;
    list[0] = 1;
    for(i = 1; i <= n; i++) a[i][1] = -1;
    while(lp--) {
        min = 2001;
        for(i = 0; list[i] !=0; i++) {
            for(j = 1; j <= n; j++) {
                if(min > a[ list[i] ][j] && a[ list[i] ][j] != -1) {
                    min = a[ list[i] ][j];
                    mini = j;
                }
            }
        }
        sum += min;
        list[i] = mini;
        for(int j = 1; j <= n; j++) a[j][mini] = -1;
    }
    
    cout<<sum<<endl;
    
    return 0;
}

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

struct edge {int u, v, cost;};

int n;
vector<edge> G;

bool comp(const edge& e1, const edge& e2) {
    return e1.cost < e2.cost;
}

class UnionFind {
 public:
    int g_num;
    vector<int> rank, par;

    UnionFind() {}
    UnionFind(int size) {
        rank.resize(size, 0);
        par.resize(size, 0);
        for (int i = 0; i < size; i++) {
            par[i] = i;
            rank[i] = 0;
        }
        g_num = size;
    }

    bool same(int x, int y) {
        return find(x) == find(y);
    }

    void unite(int x, int y) {
        x = find(x);
        y = find(y);
        if (x == y) return;

        g_num--;
        if (rank[x] > rank[y]) {
            par[y] = x;
        } else {
            par[x] = y;
            if (rank[x] == rank[y]) rank[y]++;
        }
    }

    int find(int x) {
        if (x == par[x]) return x;
        return par[x] = find(par[x]);
    }

    int group_num() {
        return g_num;
    }
};

int kruskal() {
    sort(G.begin(), G.end(), comp);
    UnionFind uf(n);
    int res = 0;
    for (auto e: G) {
        if (!uf.same(e.u, e.v)) {
            uf.unite(e.u, e.v);
            res += e.cost;
        }
    }
    return res;
}

int main(void) {
    cin >> n;
    for (int i = 0; i < n; i++) {
        for (int j = 0; j < n; j++) {
            int cost;
            cin >> cost;
            if (cost == -1) continue;
            G.push_back(edge {i, j, cost});
        }
    }
    int ans = kruskal();
    cout << ans << endl;
    return 0;
}

C++: // #define _GLIBCXX_DEBUG
#include <bits/stdc++.h>
using namespace std;
#define rep(i, n) for (int i = 0; i < (int)(n); i++)
#define all(v) v.begin(), v.end()
#define Graph vector< vector<int> >
typedef long long ll;
typedef pair<int, int> P;
const int INF = 1000000007;

int main(){
    int N;
    cin >> N;
    Graph M(N, vector<int>(N));
    rep(i, N){
        rep(j, N){
            cin >> M[i][j];
            if(M[i][j] == -1) M[i][j] = INF;
        }
    }

    vector<int> d(N, INF), p(N, -1);
    vector<bool> visited(N);
    d[0] = 0;
    p[0] = -1;
    int sum = 0;

    while(1){
        int mincost = INF;
        int u;
        rep(i, N){
            if( !visited[i] && d[i] < mincost){
                mincost = d[i];
                u = i;
            }
        }

        if(mincost == INF) break;
        sum += d[u];
        visited[u] = true;

        rep(v, N){
            if( !visited[v] && M[u][v] != INF){
                if(M[u][v] < d[v]){
                    d[v] = M[u][v];
                    p[v] = u;
                }
            }
        }
    }
    
    cout << sum << endl;

}