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

int main(void)
{
	int n, ans = 0, now = 0;
	int an[100][100], min[100];
	int flag[101];

	cin >> n;

	for(int i = 0; i < n; i++) {
		for(int j = 0; j < n; j++) {
			cin >> an[i][j];
		}
		min[i] = 2001;
		flag[i] = 0;
	}

	/* ???????則?????????即?????属????????? */
	do {
		flag[now] = 1;
		flag[100] = 0;
/*
		cout << "\n??? " << now << " ????則???????????????????" << endl;
		cout << "?????贈?????? : ";
		for(int i = 0; i < n; i++) {
			if(flag[i] == 1) {
				cout << i << " ";
			}
		}
		cout << endl;
		cout << "?????即???????属?????????則" << endl;
		for(int i = 0; i < n; i++) {
			if(flag[i] == 0) {
				cout << "??? " << i << " : " << min[i] << endl;
			}
		}
*/
		/* min?????卒??属 */
		for(int j = 0; j < n; j++) {
			if(an[now][j] != -1 && an[now][j] < min[j] && flag[j] == 0) {
/*				cout << "??? " << j <<" ???????属?????????卒??属??????????????? : "<< min[j] << " ??? " << an[now][j] << endl; */
				min[j] = an[now][j];
			}
		}
/*
		cout << "?????即???????属?????????則" << endl;
		for(int i = 0; i < n; i++) {
			if(flag[i] == 0) {
				cout << "??? " << i << " : " << min[i] << endl;
			}
		}
*/
		/* ?測??????蔵?卒蔵???min????属???? */
		int key = 2001, key_j;

		for(int j = 0; j < n; j++) {
			if(flag[j] == 0 && min[j] < key) {
				key = min[j];
				key_j = j;
			}
		}
/*
		cout << "?則???????????賊??????????????????? : ??? " << key_j << endl;
*/
		/* ?則?????????? */
		now = key_j;
		ans += key;

		/* ??????????????贈????????? */
		for(int i = 0; i < n; i++) {
			if(flag[i] == 1) {
				flag[100]++;
			}
		}
	
	}while(flag[100] != n - 1);

	cout << ans << endl;

	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];
    int i;

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

    d[0] = 0;

    while (1) {
        minv = INFTY;
        u = -1;
        for (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 (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++: #include <algorithm>
#include <iostream>
#include <string>
using namespace std;
static const int NMAX = 100;
#define INF (1 << 30)
int ADJ[NMAX][NMAX];

int main() {
  int n;
  cin >> n;
  int tmp;
  for (int i = 0; i < n; i++) {
    for (int j = 0; j < n; j++) {
      cin >> tmp;
      ADJ[i][j] = (tmp == -1) ? INF : tmp;
    }
  }

  bool visited[n];
  int edges[n];

  // add node 0
  for (int i = 0; i < n; i++) {
    edges[i] = ADJ[0][i];
    visited[i] = false;
  }
  visited[0] = true;

  int cost = 0;
  while (true) {
    int minnode = -1;
    int mincost = INF;
    // find min edge
    for (int i = 0; i < n; i++) {
      if (visited[i] == false && edges[i] < mincost) {
        minnode = i;
        mincost = edges[i];
      }
    }
    if (minnode == -1)
      break;

    // add node
    visited[minnode] = true;
    cost += mincost;

    // update connected edges
    for (int i = 0; i < n; i++) {
      edges[i] = min(edges[i], ADJ[minnode][i]);
    }
  }
  cout << cost << endl;
}