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>
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++: #if 0
AOJ??????accepted??????????????????
???????????????60??????????????§?????????

pair???????????????????????¨
????????¨?????????pair?????????????????????????????¨?????????????????????????????????
#endif

#include <iostream>
#include <algorithm>
#include <utility>
using namespace std;

int P[10010];
void init(int N){//?????????
  for (int i=0; i<=N; ++i)
    P[i]=i;
}

int root(int a){//a???root????±???????
  if(P[a]==a)
    return a;
  return (P[a]=root(P[a]));
}

bool is_same_set(int a,int b){//??????set?????????
  return root(a)==root(b);
}

void unite(int a,int b){
  P[root(a)]=root(b);
}

int main(){
  int N;
  cin>>N;
  int A[N][N];
  
  for(int i=0; i<N;i++){//????????????
    for(int j=0;j<N;j++){
      cin>>A[j][i];
    }
  }

  int M = 0; // ????????????????????°
  int num=N*N;
  int cost[num];
  int src[num],dst[num];
  for (int r=0; r<N;r++){
    for (int c=0; c<r;c++){
      if (A[r][c] > -1) {
	cost[M] = A[r][c];
	src[M] = r;
	dst[M] = c;
	M += 1;
      }
    }
  }

  pair<int,int> edge[100000];//?§??????????????????¢????????????
  for(int i=0; i<M;i++){
    edge[i]=make_pair(cost[i],i);
  }
  sort(edge,edge+M);

  int edges[M][3];
  for(int i=0; i<M;i++){//?????????????????????
    edges[i][0]=edge[i].first;
    edges[i][1]=src[edge[i].second];
    edges[i][2]=dst[edge[i].second];
  }
  /*
  check!
  for(int i=0; i<M;i++){
    cout<<"news cost="<<edges[i][0]<<" ,"<<edges[i][1]<<"-"<<edges[i][2]<<endl;
  }
  */




  init(N);
  int sum=0;
  for(int i=0; i<M;i++){//???????????????????????????
    if(is_same_set(edges[i][1],edges[i][2])==0){
      unite(edges[i][1],edges[i][2]);
      sum=sum+edges[i][0];
    }
  }
    cout<<sum<<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, mincost;
  int d[MAX], p[MAX], color[MAX];

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

  // 頂点0から始めるため
  d[0] = 0;

  while (true)
  {
    mincost = INFTY;
    u = -1;
    // 初回は頂点0が選ばれる
    // 隣接する頂点を探す処理で、重みdが設定されていれば
    // 最小コストの頂点uが選ばれる
    for (int i = 0; i < n; i++)
    {
      if (mincost > d[i] && color[i] != BLACK)
      {
        u = i;
        mincost = d[i];
      }
    }

    if (u == -1)
    {
      break;
    }

    // 最小全域木の頂点に選ばれた
    color[u] = BLACK;

    for (int v = 0; v < n; v++)
    {
      if (color[v] != BLACK && M[u][v] != INFTY)
      {
        // 最小全域木に選ばれていないかつ、uに対して辺がある頂点v
        if (d[v] > M[u][v])
        {
          // 頂点uとvの辺の重みに更新する
          d[v] = M[u][v];
          p[v] = u;
          color[v] = GRAY;
        }
      }
    }
  }

  // 最小全域木の辺の重みの総和
  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;
}