Go: package main

import (
	"fmt"
	"sort"
)

type Edge struct {
	I int
	J int
	A int
}

func main() {
	var n int
	fmt.Scan(&n)

	g := make([][]int, n)
	edges := make([]Edge, 0, n*(n-1)/2)
	parents := make([]int, n)
	for i := 0; i < n; i++ {
		g[i] = make([]int, n)
		for j := 0; j < n; j++ {
			fmt.Scan(&g[i][j])
			if g[i][j] > 0 {
				edges = append(edges, Edge{i, j, g[i][j]})
			}
		}
		parents[i] = i
	}
	sort.SliceStable(edges, func(i, j int) bool { return edges[i].A > edges[j].A })

	sum := 0
	for len(edges) > 0 {
		edge := edges[len(edges)-1]
		edges = edges[:len(edges)-1]

		if same(edge.I, edge.J, &parents) {
			continue
		}
		union(edge.I, edge.J, &parents)
		sum += edge.A
	}
	fmt.Println(sum)
}



func root(id int, parents *[]int) int {
	if id == (*parents)[id] {
		return id
	}
	return root((*parents)[id], parents)
}

func union(i, j int, parents *[]int) {
	(*parents)[root(j, parents)] = (*parents)[root(i, parents)]
}

func same(i, j int, parents *[]int) bool {
	return root(i, parents) == root(j, parents)
}

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

int n;
int g[101][101];

int d[101];
char c[101];
int p[101];

void prim() {
    for (int i = 0; i < n; ++i) {
        d[i] = INT_MAX;
        c[i] = 'w';
    }
    c[0] = 'b';
    d[0] = 0;
    while (true) {
        int u, v;
        int mine = INT_MAX;
        for (int j = 0; j < n; ++j) {
            if (c[j] == 'b') {
                u = j;
                for (int k = 0; k < n; ++k) {
                    if(g[u][k] > -1 && g[u][k] <= d[k] && c[k] != 'b' && g[u][k] <= mine) {
                        d[k] = g[u][k];
                        mine = d[k];
                        v = k;
                    }
                }
            }
        }
        p[v] = u;
        c[v] = 'b';
        if(mine == INT_MAX) break;
    }
}

int main() {
    cin >> n;
    for (int i = 0; i < n; ++i) {
        for (int j = 0; j < n; ++j) {
            int w;
            cin >> w;
            g[i][j] = w;
        }
    }
    prim();
    int sum;
    for (int k = 0; k < n; ++k) {
        sum += d[k];
    }
    cout << sum << endl;


    return 0;
}

C++: //最少全域木
#include<iostream>
#include<vector>
#include<algorithm>
using namespace std;
int G[103][103];
int V;
int NG[103][103];//新しくできるほう
int used[103];
int main(){
	int ans=0;
	cin>>V;
	for(int i=0;i<V;i++){
		for(int j=0;j<V;j++){
		cin>>G[i][j];
		}
	}
	for(int i=0;i<103;i++)for(int j=0;j<103;j++)NG[i][j]=-1;
	used[0]=1;
	for(int i=0;i<V;i++){
		int u=-1,a,b;
		for(int j=0;j<V;j++){
		if(used[j]==0)u=i;
		}
		if(u==-1)break;
		int now=99999999;
		for(int j=0;j<V;j++){
			for(int k=0;k<V;k++){
			if(now>G[j][k]&&G[j][k]!=-1&&used[j]==1&&used[k]==0){
			now=G[j][k];
			a=j,b=k;
			}
			}
		}
		ans+=G[a][b];
		used[b]=1;
		NG[a][b]=G[a][b];
	}
	cout<<ans<<endl;
	return 0;
}

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

const int white = 0;
const int gray = 1;
const int black = 2;
const int Max_n = 100;
const int Max_a = 2000;

int M[Max_n][Max_n];
int color[Max_n], d[Max_n], p[Max_n];
int n;

int prim(){
    for(int i=n; i<n; i++){
        color[i] = white;
        d[i] = Max_a + 1;
    }

    d[0] = 0;
    p[0] = -1;

    while(1){
        int mincost = Max_a + 1;
        int u;
        for(int i=0; i<n; i++){
            if(color[i] != black && d[i] < mincost){
                mincost = d[i];
                u = i;
            }
        }
        if(mincost == Max_a + 1){
            break;
        }

        color[u] = black;

        for(int v=0; v<n; v++){
            if(color[v] != black && M[u][v] != -1){
                if(M[u][v] < d[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++){
            cin >> M[i][j];
        }
    }

    cout << prim() << endl;


    return 0;
}

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

#define rep(i, a, b) for (int i = (a); i < (int)(b); i++)
#define rrep(i, a, b) for (int i = (a); i >= (int)(b); i--)
#define all(x) (x).begin(), (x).end()
using i32 = int32_t;
using i64 = int64_t;
using f32 = float;
using f64 = double;
using P   = pair<int, int>;

template <class T>
bool chmin(T& a, T b) {
    if (a > b) {
        a = b;
        return true;
    } else {
        return false;
    }
}
template <class T>
bool chmax(T& a, T b) {
    if (a < b) {
        a = b;
        return true;
    } else {
        return false;
    }
}

template <class T>
void dump_vec(const vector<T>& v) {
    auto len = v.size();
    rep(i, 0, len) {
        cout << v[i] << (i == (int)len - 1 ? "\n" : " ");
    }
}

struct FastIO {
    FastIO() {
        cin.tie(0);
        ios::sync_with_stdio(false);
        cout << fixed << setprecision(20);
    }
} FASTIO;

//---------------------------------------------------------------------------------------------------

struct Edge {
    int from, to;
    i64 cost;
    Edge() {}
    Edge(int t, i64 c) : from(-1), to(t), cost(c) {}
    Edge(int f, int t, i64 c) : from(f), to(t), cost(c) {}

    bool operator<(const Edge& r) const {
        return cost < r.cost;
    }
    bool operator>(const Edge& r) const {
        return cost > r.cost;
    }
};

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

// 無向
void link(Graph& g, int from, int to, int cost = 1) {
    g[from].push_back(Edge(from, to, cost));
    g[to].push_back(Edge(to, from, cost));
    return;
}

// 有向
void connect(Graph& g, int from, int to, int cost = 1) {
    g[from].push_back(Edge(from, to, cost));
    return;
}

pair<i64, Vertex> minimum_spanning_tree(const Graph& g, int start) {
    i64 total_cost = 0;
    Vertex V;
    vector<bool> visited(g.size(), false);

    priority_queue<Edge, vector<Edge>, greater<Edge>> que;
    que.push(Edge(start, start, 0));
    while (!que.empty()) {
        const auto e = que.top();
        que.pop();
        if (visited[e.to]) continue;

        visited[e.to] = true;
        V.push_back(e);
        total_cost += e.cost;
        for (const auto& n : g[e.to]) {
            if (!visited[n.to]) {
                que.push(n);
            }
        }
    }
    return make_pair(total_cost, V);
}

//---------------------------------------------------------------------------------------------------

signed main() {
    int N;
    cin >> N;
    Graph G(N);
    rep(i, 0, N) rep(j, 0, N) {
        int w;
        cin >> w;
        if (w >= 0) {
            connect(G, i, j, w);
        }
    }
    auto ans = minimum_spanning_tree(G, 0);
    cout << ans.first << "\n";
}