Go: package main

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

var scanner = bufio.NewScanner(os.Stdin)

func nextString() string {
	scanner.Scan()
	return scanner.Text()
}

func nextInt() int {
	n, err := strconv.Atoi(nextString())
	if err != nil {
		fmt.Printf("strconv.Atoi failed: %v\n", err)
	}
	return n
}

type ElementKey int
type Node struct {
	key    ElementKey
	parent *Node
	rank   int
}

func newNode(key ElementKey) *Node {
	node := Node{}
	node.key = key
	node.parent = &node
	node.rank = 0

	return &node
}

func union(x, y *Node) {
	xSet := findSet(x)
	ySet := findSet(y)
	link(xSet, ySet)
}

func link(x, y *Node) {
	if x.rank > y.rank {
		y.parent = x
	} else {
		x.parent = y

		if x.rank == y.rank {
			y.rank++
		}
	}
}

func findSet(x *Node) *Node {
	if x != x.parent {
		x.parent = findSet(x.parent)
	}
	return x.parent
}

func newDisjointSets(nSets int) *DisjointSets {
	sets := DisjointSets{}
	sets.keyToNode = map[ElementKey]*Node{}
	for i := 0; i < nSets; i++ {
		key := ElementKey(i)
		sets.keyToNode[key] = newNode(key)
	}
	return &sets
}

type DisjointSets struct {
	keyToNode map[ElementKey]*Node
}

func (sets *DisjointSets) union(x, y ElementKey) {
	xNode := sets.keyToNode[x]
	yNode := sets.keyToNode[y]
	union(xNode, yNode)
}

func (sets DisjointSets) findSet(x ElementKey) *Node {
	xNode := sets.keyToNode[x]
	return findSet(xNode)
}

type Edge struct {
	i, j   int
	weight int
}

func main() {
	scanner.Split(bufio.ScanWords)

	n := nextInt()
	sets := newDisjointSets(n)
	edges := []Edge{}
	a := make([][]int, n)
	for i := 0; i < n; i++ {
		a[i] = make([]int, n)
		for j := 0; j < n; j++ {
			a[i][j] = nextInt()
			if a[i][j] >= 0 {
				e := Edge{
					i:      i,
					j:      j,
					weight: a[i][j],
				}
				edges = append(edges, e)
			}
		}
	}
	sort.Slice(edges, func(i, j int) bool { return edges[i].weight < edges[j].weight })
	totalWeight := 0
	for _, edge := range edges {
		i := ElementKey(edge.i)
		j := ElementKey(edge.j)
		if sets.findSet(i) != sets.findSet(j) {
			totalWeight += edge.weight
			sets.union(i, j)
		}
	}
	fmt.Println(totalWeight)
}

C++: #include <iostream>
 
using namespace std;
 
 
class Graph{
private:
 
  int size;
  int **graph;
 
public:
 
  Graph(int size){
    int i;
    int j;
    this->size = size;
    this->graph = new int*[size];
    for(i = 0;i < size;i++){
      this->graph[i] = new int[size];
    }
  }
 
  ~Graph(){
    int i;
    for(i = 0;i < this->size;i++){
      delete[] this->graph[i];
    }
    delete[] this->graph;
  }
 
  int getMinimum(){
    int i;
    int j;
    int min;
    int res = 0;
    int *state;

    state = new int[this->size];


    for(i = 0;i < this->size;i++){
      state[i] = 100000000;
    }
 
    for(i = 0;i < this->size;i++){
 
      for(j = 1;j < this->size;j++){
	if(graph[i][j] > 0 && graph[i][j] < state[i]){
	  state[i] = graph[i][j];
	}
      }
    }

    for(i = 0;i < this->size;i++){
      res += state[i];
    }

    return res-1;
  }
 
  void setValue(int x,int y,int value){
    this->graph[x][y] = value;
  }
 
};
 
int main(){
 
  int i;
  int j;
  int n;
  int a;
 
  Graph *graph;
 
  cin >> n;
 
  graph = new Graph(n);
 
  for(i = 0;i < n;i++){
    for(j = 0;j < n;j++){
      cin >> a;
      graph->setValue(i,j,a);
    }
  }
 
  cout << graph->getMinimum() << endl;
 
  delete graph;
 
  return 0;

}

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

static const int MAX = 100;
static const int INFTY = (1<<21);
static const int WHITE = 0;
static const int GRAY = 1;
static const int BLACK = 2;

int n, M[MAX][MAX];

int prim(){
  int u, minv;
  int d[MAX], p[MAX], color[MAX];

  for(int i=0;i<n;i++){
    d[i] = INFTY;
    p[i] = -1;
    color[i] = WHITE;
  }

  d[0] = 0;

  while(1){
    minv = INFTY;
    u = -1;
    for(int i=0;i<n;i++){
      if(minv > d[i] && color[i] != BLACK){
        u=i;
        minv = d[i];
      }
    }
    if(u==-1)
      break;
    
    color[u] = BLACK;

    for(int v=0;v<n;v++){
      if(color[v] != BLACK && M[u][v]!=INFTY){
        if(d[v]>M[u][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++){
      int e;
      cin >> e;
      M[i][j] = (e==-1)?INFTY :e;
    }
  }
  cout << prim() << endl;
  return 0;
}

C++: //
// Created by tattsun on 2017/02/16.
//

#include <iostream>

#define MAX_N 101
#define INFTY 20000
#define NIL -1

enum Color {
    White,
    Glay,
    Black,
};

using namespace std;

int n;
int w[MAX_N][MAX_N];
int d[MAX_N], p[MAX_N];
Color color[MAX_N];

int min(int x, int y) {
    if(x < y) return x;
    return y;
}

int solve() {
    d[0] = 0;

    while(true) {
        int u = NIL, c = INFTY;

        for(int i=0; i<n; i++) {
            if(d[i] < c && color[i] != Black) {
                u = i;
                c = d[i];
            }
        }

        if(u == NIL)
            break;

        color[u] = Black;

        for(int i=0; i<n; i++) {
            if(color[i] != Black && w[u][i] != INFTY) {
                if(d[i] > w[u][i]) {
                    d[i] = w[u][i];
                    p[i] = u;
                    color[i] = Glay;
                }
            }
        }
    }


    int tc = 0;
    for(int i=0; i<n; i++) {
        if(color[i] == Black) {
            tc += w[i][p[i]];
        }
    }
    return tc;
}

int main() {
    for (int i = 0; i < MAX_N; i++) {
        d[i] = INFTY;
        p[i] = INFTY;
        color[i] = White;
        for (int j = 0; j < MAX_N; j++)
            w[i][j] = INFTY;
    }

    int p;
    cin >> n;
    for (int i = 0; i < n; i++) {
        for (int j = 0; j < n; j++) {
            cin >> p;
            w[i][j] = (p == -1) ? INFTY : p;
        }
    }

    cout << solve() << endl;
}

C++: #define _CRT_SECURE_NO_WARNINGS
#define _USE_MATH_DEFINES
#include <iostream>
using namespace std;
const int num = 100;
int v[num][num], n, c[num], p[num], d[num];;
inline int mini(int k) {
	for (int i = 0; i < n; i++) {
		d[i] = 99999999;
	}

	d[k] = 0;
	p[k] = -1;
	while (1) {
		int minv = 99999999, u = -1;
		for (int i = 0; i < n; i++) {
			if (d[i] < minv && c[i] == 0) {
				minv = d[i];
				u = i;
			}
		}
		if (u == -1) break;
		for (int i = 0; i < n; i++) {
			if (v[u][i] != -1 && c[i] == 0) {
				if (d[i] > v[u][i]) {
					d[i] = v[u][i];
					p[i] = u;
				}
			}
		}
		c[u] = 1;
	}
	int sum = 0;
	for (int i = 0; i < n; i++) {
		if(p[i] != -1) sum += v[i][p[i]];
	}
	return sum;
}
int main() {
	cin >> n;
	for (int i = 0; i < n; i++) {
		for (int j = 0; j < n; j++) {
			cin >> v[i][j];
		}
	}
	for (int i = 0; i < n; i++) {
		c[i] = 0;
	}
	cout << mini(0) << endl;
	return 0;
}

C++: #include <algorithm>
#include <iostream>
#include <set>
#include <vector>
#define FOR(i,k,n) for (int (i)=(k); (i)<(n); ++(i))
#define REP(i,n) FOR(i,0,n)
#define pb push_back
#define mp make_pair
#define fst first
#define snd second
#define all(v) begin(v), end(v)
using namespace std;
typedef pair<int,int> PII;

int P[100]; //union_find

int root(int i){
    if(P[i] == i) return i;
    else return P[i] = root(P[i]);
}

bool same(int x, int y){
    return root(P[x]) == root(P[y]);
}

void unite(int x, int y){
    P[root(x)] = root(y);
}

int main(){
    int n;
    cin >> n;
    int g[n][n];
    vector<pair<int,PII>> V;
    REP(i,n){
        REP(j,n){
            cin >> g[i][j];
            if(i<j && g[i][j] >= 0) V.pb(mp(g[i][j],mp(i,j)));
        }
    }
    sort(all(V));
    REP(i,n){
        P[i] = i;
    }
    int wsum=0;
    REP(i,n-1){
        int x = V[i].snd.fst;
        int y = V[i].snd.snd;
        if(!same(x,y)){
            unite(x,y);
            wsum += V[i].fst;
        }
    }

    cout <<wsum<<endl;

    return 0;
}