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 <bits/stdc++.h>
using namespace std;

static const int N = 100;
static const int INF = (1 << 30);
static const int WHITE = 0;
static const int GRAY = 1;
static const int BLACK = 2;


int n;
int m[N][N];

int prim(){
    int u,min_val;
    int d[N],p[N],color[N];

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

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

        if(u == -1) break;
        color[u] = BLACK;
        for(int v=0;v<n;v++){
            if(color[v] != BLACK && m[u][v] != INF){
                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;
}


//mainは問題なし
int main(){
    int in_val;
    cin >> n;
    for(int i=0;i<n;i++){
        for(int j=0;j<n;j++){
            cin >> in_val;
            if(in_val == -1)
                in_val = INF;
            m[i][j] = in_val;
        }
    }

    cout << prim() << endl;

}

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

const static int MAX = 100;
const static int INFTY = (1<<21);
const static int WHITE = 0;
const static int GRAY = 1;
const static 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(true){
    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 work;
      cin >> work;
      M[i][j] = (work == -1) ? INFTY : work;
    }
  }

  cout << prim() << endl;


  return 0;
}

C++: #include <iostream>
#include <queue>
#define INF 200000
using namespace std;
typedef pair<int,int> P;
P a;
priority_queue< P,vector<P> ,greater<P> > pq;
int map[101][101];
bool decided[101];
int sum,n;
int node,count;
void check(){
	node=1;
	decided[node]=true;
	count=n-1;
	while(1){
		for(int i=1;i<=n;i++){
			if(map[node][i]!=-1&&!decided[i]){
				a=make_pair(map[node][i],i);
				pq.push(a);
			}
		}
		while(decided[pq.top().second])pq.pop();
		sum+=pq.top().first;
		node=pq.top().second;
		decided[node]=true;
		count--;
		if(count==0)break;
		pq.pop();
	}
}

int main(){
	cin >>n;
	for(int i=1;i<=n;i++){
		for(int j=1;j<=n;j++){
			cin >> map[i][j];
		}
	}
	sum=0;
	check();
	cout << sum<<endl;
}