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<cstdio>
#include<cstring>
#include<map>
#include<vector>
#include<queue>
using namespace std;

struct Edge{
  int src,dst;
  int weight;
  Edge(int src,int dst,int weight):
    src(src),dst(dst),weight(weight){}
};

typedef vector<Edge> Edges;
typedef vector<Edges> Graph;

bool operator < (const Edge &m,const Edge &n){
  return m.weight!=n.weight ? m.weight>n.weight :
    m.src!=n.src ? m.src>n.src : m.dst>n.dst;
}

struct UnionFind{
  vector<int> data;
  UnionFind(int size):
    data(size,-1){}

  int root(int x){
    return data[x]<0 ? x :
      data[x]=root(data[x]);
  }

  void unionset(int x,int y){ //bool->void
    x=root(x);y=root(y);
    if(x!=y){
      if(data[y]<data[x])
	swap(x,y);
      data[x]+=data[y];
      data[y]=x;
    }
    //return x!=y;
  }

  bool findset(int x,int y){
    return root(x)==root(y);
  }
};

/*test用関数
void PrintGraph(Graph);
void PrintEdges(Edges);
void PrintPriority_queue(priority_queue<Edge>);
*/

pair<int,Edges> MinimumSpinningForest(Graph g){
  int n=g.size();
  UnionFind uf(n);
  priority_queue<Edge> que;

  for(int i=0;i<n;i++){
    for(Edges::iterator l=g[i].begin();l!=g[i].end();l++){
      if((*l).src<(*l).dst && (*l).weight>0)
	que.push(*l);
    }
  }

  //PrintPriority_queue(que);
  int sum=0;
  Edges select;

  while((int)select.size()<n && !que.empty()){
    Edge tmp=que.top();que.pop();

    if(!uf.findset(tmp.src,tmp.dst)){
      uf.unionset(tmp.src,tmp.dst);
      select.push_back(tmp);
      sum+=tmp.weight;
    }
  }

  return pair<int,Edges>(sum,select);
}


int main(int argc,char* argv[]){
  Graph g;
  int n,x;
  pair<int,Edges> p;

  cin>>n; 
  for(int i=1;i<=n;i++){
    for(int l=1;l<=n;l++){
      cin>>x;
      Edge tmp(i,l,x);
      Edges input;input.push_back(tmp);
      g.push_back(input);
    }
  }

  //PrintGraph(g);

  p=MinimumSpinningForest(g);

  //PrintEdges(p.second);
  
  cout<<p.first<<endl;
  return 0;
}

C++: # include<iostream>
using namespace std;
const int MAX = 100;
const int INFTY = (1 << 21);
const int WHITE = 0;
const int GREY = 1;
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 (color[i] != BLACK && minv > d[i]) {
				minv = d[i];
				u = 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] = GREY;
				}
			}
		}
	}

	int sum = 0;
	for (int i = 0; i < n; i++) {
		if (p[i] != -1) sum += d[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++: #include<iostream>
#include<vector>
#include<algorithm>
#include<queue>
#include<cstring>
#define P pair<int , int>
using namespace std;

int main(){
  int n, a[109][109];
  bool check[109];
  priority_queue<P, vector<P>, greater<P> > Q;
  cin >> n;
  for(int i=0;i<n;i++){
    for(int j=0;j<n;j++)cin >> a[i][j];
  }
  memset(check, false, sizeof(check));
  int ans = 0;
  Q.push(P(0, 0));
  while(!Q.empty()){
    P p = Q.top();Q.pop();
    if(check[p.second])continue;
    ans += p.first;
    check[p.second] = true;
    for(int i=0;i<n;i++){
      if(!check[i] && a[p.second][i]!=-1){
        Q.push(P(a[p.second][i], i));
      }
    }
  }
  cout << ans << endl;
}

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;
}