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<bits/stdc++.h>
using namespace std;

#define rep(i,n) for(int i = 0; i < n; i++)
#define Rep(i,n) for(int i = 1; i <= n; i++)
#define sz(x) int(x.size())
#define all(v) v.begin(), v.end()
#define rall(v) v.rbegin(), v.rend()
#define YesorNo(a) printf(a ? "Yes\n" : "No\n")
#define endl '\n'
#define fi first
#define se second
using ll = long long;
using P = pair<int,int>;
using Pl = pair<ll,ll>;
template<class T> using V = vector<T>;
const int dx[] = {0,1,0,-1,1,1,-1,-1};
const int dy[] = {1,0,-1,0,1,-1,-1,1};
const int inf = (1<<30)-1;
const ll infll = (1LL<<62)-1;
ll ceil(const ll &a, const ll &b){return ((a)+(b)-1)/b;}
template<class T> inline bool chmin(T& a, T b) { if (a > b) { a = b; return true; } return false; }
template<class T> inline bool chmax(T& a, T b) { if (a < b) { a = b; return true; } return false; }

ll MinimumSpanningTree(const V<V<pair<ll, int>>> &g, int n) { // 最小全域木
    using pi = pair<ll,int>; // pair = (cost, to);
    ll res = 0;

    vector<int> v;
    v.push_back(0);
    priority_queue<pi, vector<pi>, greater<pi>> pq; 
    vector<bool> seen(n);
    seen[0] = true;
    for(pi nv : g[0]) {
        pq.push(nv);
    }

    while(sz(v) != n) {
        pi p = pq.top(); pq.pop();
        if(seen[p.se]) continue;
        v.push_back(p.se);
        seen[p.se] = true;
        res += p.fi;
        for(pi nv : g[p.se]) {
            if(!seen[nv.se])
                pq.push(nv);
        }
    }
    return res;
}

int main(){
    int n;
    cin >> n;
    V<V<pair<ll,int>>> g(n);
    rep(i,n)rep(j,n) {
        ll a;
        cin >> a;
        if(a == -1) continue;
        g[i].emplace_back(a,j);
    }
    ll ans = MinimumSpanningTree(g,n);
    cout << ans << endl;
}

C++: #include <cstdio>
#include <climits>
#include <vector>

int w[100][100];
std::vector<int> mst;
std::vector<int> others;
typedef std::vector<int>::iterator itr;

int minimum(){
    if(others.size()<=0)return 0;
    int candiW=INT_MAX;
    itr candiI;
    for(itr i=mst.begin();i!=mst.end();i++){
        for(itr j=others.begin();j!=others.end();j++){
            if(w[*i][*j]<candiW){
                candiW = w[*i][*j];
                candiI = j;
            }
        }
    }
    mst.push_back(*candiI);
    printf("%d ",*candiI);
    others.erase(candiI);
    return candiW + minimum();
}

int main(){
    int i, j, n;
    scanf("%d",&n);
    for(i=0;i<n;i++){
        for(j=0;j<n;j++){
            scanf("%d",&w[i][j]);
            if(w[i][j]==-1)w[i][j]=INT_MAX;
        }
    }
    mst.push_back(0);
    for(i=1;i<n;i++)others.push_back(i);
    printf("%d\n",minimum());
    return 0;
}

C++: #include <bits/stdc++.h>
using namespace std;
struct cww{cww(){ios::sync_with_stdio(false);cin.tie(0);}}star;
#define P(x) cout << (x) << '\n'
#define p(x) cout << (x)
#define all(c) (c).begin(), (c).end()
#define rall(c) (c).rbegin(), (c).rend()
#define vv(type, c, m, n, i) vector<vector<type>> c(m, vector<type>(n, i));
#define rep(i,a,n) for(int i=(a), i##_len=(n); i<i##_len; ++i)
#define rrep(i,a,n) for(int i=(a), i##_len=(n); i>i##_len; --i)
#define len(x) ((int)(x).size())
#define mp make_pair
#define eb emplace_back
typedef long long ll;
typedef vector<int> vi;
typedef vector<double> vd;
typedef vector<long long> vll;
typedef vector<string> vs;
typedef vector<bool> vb;
constexpr int MAX = 101;
constexpr int INF = 1<<21;
enum Color { WHITE = 0, GRAY, BLACK };
int n;
vv(int, M, MAX, MAX, INF);
inline int prim() {
	vi color(n, WHITE);
	int d[n];
	d[0] = 0;
	rep(i, 1, n) d[i] = INF;
    int minv, u;
    while(true) {
        minv = INF;
        u = -1;
        rep(i, 0, n) {
            if(minv > d[i] && color[i] != BLACK) {
                u = i;
                minv = d[i];
            }
        }
        if(u == -1) break;
        color[u] = BLACK;
        rep(v, 0, n) {
            if(color[v] != BLACK && d[v] > M[u][v]) {
                d[v] = M[u][v];
                color[v] = GRAY;
            }
        }
    }
    return accumulate(all(d), 0);
}
int main() {
    cin >> n;
    int e;
    rep(i, 0, n) {
        rep(j, 0, n) {
            cin >> e;
            if(e != -1) M[i][j] = e;
        }
    }
    P(prim());
    return 0;
}

C++: #include <iostream>

using namespace std;

int n;
int adja[100][100];

int spanning() {
    int visit[100] = {}, cost = 0;
    visit[0] = 1;
    while (1) {
        int minj, minc = 2001;
        for (int i = 0; i < n; ++i) {
            if (visit[i]) {
                for (int j = 0; j < n; ++j) {
                    if (adja[i][j] >= 0 && !visit[j] && minc > adja[i][j]) {
                        minc = adja[i][j];
                        minj = j;
                    }
                }
            }
        }
        if (minc == 2001)
            break;
        cost += minc;
        visit[minj] = 1;
    }
    return cost;
}

int main() {
    cin >> n;
    for (int i = 0; i < n; ++i) {
        for (int j = 0; j < n; ++j) {
            cin >> adja[i][j];
        }
    }
    cout << spanning() << endl;

    return 0;
}

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

int x[10000][10000];
int MIN[10000];
int MINX = 0;
int MINZ = 10000000;

int main() {
	memset(MIN, 127, sizeof(MIN));
	int n, a;
	cin >> n;
	for (int i = 0; i < n; i++) {
		for (int j = 0; j < n; j++) {
			cin >> a;
			x[i][j] = a;
		}
	}
	for(int i=0;i<n;i++){
	    for(int j=0;j<n;j++){
	        if(x[i][j]!=-1){
	            MIN[i]=min(x[i][j],MIN[i]);
	        }
	    }
	}
	for(int i=0;i<n;i++){
	    MINX=0;
	    for(int j=0;j<n;j++){
	        MINX += min[j];
	    }
	    MINZ=min(MINZ,MINX);
	}
	cout<<MINZ<<endl;
	return 0;
}

C++: #include<stdio.h>

static const int MAX = 500;
static const int INFTY = (1<<21);

main(){
  int n, i, j, e, sum,M[MAX][MAX]={0};
  int u,minV,INT_MAX,A[MAX]={INFTY},key[MAX]={INFTY};
  /*

    your code


   */

  scanf("%d", &n);
  
  for ( i = 0; i< n; i++ ){
    for ( j = 0; j < n; j++ ){
      scanf("%d", &e);
      M[i][j] = (e==-1)?INFTY:e;
    }
  }
  
  
  while(1){
    minV = 
      for(i=1;i<=n;i++){
        if((i < minV) && 

  






















  sum = 0;

  for ( i = 0; i < n; i++ ){
    if ( p[i] != -1 ) sum += M[i][p[i]];
  }

  printf("%d\n", sum);

  retur
}