Go: package main

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

// Define disjoint-set forests

type vertexNo int

type vertex struct {
	number vertexNo
	rank int
	parent *vertex
}

func makeSet(number vertexNo) vertex {
	return vertex {
		number: number,
		rank: 0,
		parent: nil,
	}
}

func union(x, y *vertex) *vertex {
	return link(findSet(x), findSet(y))
}

func link(x, y *vertex) *vertex {
	if x.rank > y.rank {
		y.parent = x
		return x
	} else {
		x.parent = y
		if x.rank == y.rank {
			y.rank += 1
		}
		return y
	}
}

func findSet(v *vertex) *vertex {
	if v.parent == nil {
		return v
	}
	v.parent = findSet(v.parent)
	return v.parent
}

// Function to calculate minimum spanning tree

type matrix [][]int

type edge struct {
	one vertexNo
	two vertexNo
	weight int
}

const(
	MAX_VERTICES = 100
)

func newEdgesFromMatrix(matrix matrix) []edge {
	edges := make([]edge, 0, MAX_VERTICES * MAX_VERTICES)

	for i := 0; i < len(matrix); i++ {
		row := matrix[i]
		for j := i; j < len(row); j++ {
			if row[j] >= 0 {
				edge := edge{one: vertexNo(i+1), two: vertexNo(j+1), weight: row[j]}
				edges = append(edges, edge)
			}
		}
	}

	return edges
}

func solve(matrix matrix) int {
	nVertices := len(matrix)

	// initialize vertices
	vertices := make([]vertex, nVertices)
	for i := 0; i < nVertices; i++ {
		vertices[i] = makeSet(vertexNo(i+1))
	}

	// prepare edges sorted in the ascending order of weight
	edges := newEdgesFromMatrix(matrix)
	sort.Slice(edges, func(i, j int) bool {
		return edges[i].weight < edges[j].weight
	})

	unionCount := 0
	weightSum := 0
	for unionCount < nVertices-1 {
		for i := 0; i < len(edges); i++ {
			edge := edges[i]
			v1 := &vertices[edge.one-1]
			v2 := &vertices[edge.two-1]
			rep1 := findSet(v1)
			rep2 := findSet(v2)
			if rep1.number == rep2.number {
				continue
			}
			union(rep1, rep2)
			edges = append(edges[0:i], edges[i+1:]...)
			weightSum += edge.weight
			unionCount++
			break
		}
	}

	return weightSum
}

// main

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

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

	matrix := parseMatrix(n, sc)

	edges := newEdgesFromMatrix(matrix)
	sort.Slice(edges, func(i, j int) bool {
		return edges[i].weight < edges[j].weight
	})

	fmt.Println(solve(matrix))
}

func parseMatrix(n int, sc *bufio.Scanner) [][]int {
	matrix := make([][]int, n)
	for i := 0; i < n; i++ {
		matrix[i] = make([]int, n)
		for j := 0; j < n; j++ {
			x, err := nextInt(sc)
			if err != nil {
				panic(err)
			}
			matrix[i][j] = x
		}
	}
	return matrix
}

func nextText(sc *bufio.Scanner) string {
	sc.Scan()
	return sc.Text()
}

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

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

#define INF 1<<21
#define BLACK 0
#define GRAY 1
#define WHITE 2

int prim(int n, int **A, int *d, int *p) {
  int *color = new int[n];

  for (int i = 0; i < n; i++) {
    color[i] = WHITE;
    d[i] = INF;
  }

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

  while (true) {
    int mincost = INF;
    int u;
    for (int i = 0; i < n; i++) {
      if ((color[i] != BLACK) && (d[i] < mincost)) {
        mincost = d[i];
        u = i;
      }
    }

    if (mincost == INF) {
      break;
    }

    color[u] = BLACK;

    for (int v = 0; v < n; v++) {
      if ((color[v] != BLACK) && (A[u][v] != INF)) {
        if (A[u][v] < d[v]) {
          d[v] = A[u][v];
          p[v] = u;
          color[v] = GRAY;
        }
      }
    }

  }

  delete color;

  return 0;
}

int main() {
  int n;
  cin >> n;

  int **A = new int*[n];
  for (int i = 0; i < n; i++) {
    A[i] = new int[n];
  }

  for (int i = 0; i < n; i++) {
    for (int j = 0; j < n; j++) {
      int w;
      cin >> w;
      if (w == -1) {
        A[i][j] = INF;
      }
      else {
        A[i][j] = w;
      }
    }
  }

  int *d = new int[n];
  int *p = new int[n];
  prim(n, A, d, p);

  int sum = 0;
  for (int i = 0; i < n; i++) {
    sum += d[i];
  }

  cout << sum << endl;

  for (int i = 0; i < n; i++) {
    delete[] A[i];
  }
  delete[] A;

  delete d;
  delete p;

  return 0;
}

C++: #include <iostream>
#include <algorithm>
#include <vector>

using namespace std;

struct Path{
    int w,s,t;
    
    bool operator < (const Path &a) const{
        return w < a.w;
    }
};

struct UnionFind{
    vector<int> par;
    
    UnionFind(int n)
        :par(n)
    {
        for(int i=0;i<n;i++){
            par[i]=i;
        }
    }
    
    void unite(int x,int y){
        int rx=root(x),ry=root(y);
        if(rx==ry)return;
        else{
            par[rx]=ry;
            return;
        }
    }
    
    int root(int x){
        if(x==par[x])return x;
        else return par[x]=root(par[x]);
    }
};

int main(void){
    int i,j,n,w;
    vector<Path> path;
    Path tmp;
    
    cin>>n;
    for(i=0;i<n;i++){
        for(j=0;j<n;j++){
            cin>>w;
            if(i>j)continue;
            else if(w!=-1){
                tmp.w=w,tmp.s=i,tmp.t=j;
                path.push_back(tmp);
            }
        }
    }
    
    sort(path.begin(),path.end());
    
    UnionFind tree(n);
    int sum=0;

    for(i=0;i<path.size();i++){
        tmp=path[i];
        if(tree.root(tmp.s)!=tree.root(tmp.t)){
            tree.unite(tmp.s,tmp.t);
            sum+=tmp.w;
        }
    }

    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
//------------------------------------------
#include <iostream>
#include <vector>
#include <list>
#include <map>
#include <set>
#include <queue>
#include <deque>
#include <stack>
#include <bitset>
#include <algorithm>
#include <functional>
#include <numeric>
#include <utility>
#include <sstream>
#include <iomanip>
#include <cstdio>
#include <cmath>
#include <cstdlib>
#include <cctype>
#include <string>
#include <cstring>
#include <ctime>
#include <limits>
using namespace std;

//repetition
//------------------------------------------
#define FOR(i,a,b) for(int i=(a);i<(b);i++)
#define FORR(i,a,b) for(int i=(a);i>(b);i--)
#define REP(i,n)  FOR(i,0,n)

//conversion
//------------------------------------------
inline int toInt(string s) {int v; istringstream sin(s);sin>>v;return v;}
template<class T> inline string toString(T x) {ostringstream sout;sout<<x;return sout.str();}

//debug
//-------------------------------------------
#define dump(x)  cerr << #x << " = " << (x) << endl;
#define debug(x) cerr << #x << " = " << (x) << " (L" << __LINE__ << ")" << " " << __FILE__ << endl;
#define INF std::numeric_limits<int>::max()

//typedef
//-------------------------------------------
typedef long long ll;

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

int prim(int used, int sum) {
    if (used == 0) return sum;

    int tmp = INF;
    int use = -1;
    REP(i, n) {
        if ((used>>i)&1) {
            continue;
        }
        REP(j, n) {
            if (((used>>j)&1) && g[i][j] < tmp) {
                tmp = g[i][j];
                use = j;
            }
        }
    }
    return prim(used&(~(1<<use)), sum + tmp);
}

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

    cin >> n;
    REP(i, n) REP(j, n) {
        cin >> g[i][j];
        if (g[i][j] < 0) g[i][j] = INF;
    }
    int used = (1<<n) - 1;
    cout << prim(used&(~1), 0) << endl;

    return 0;
}