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++: // 最小全域木 ( プリム法 )
#include<cstdio>
#include<cstdlib>
#include<cstring>
#include<stack>
#include<algorithm>
#include<iostream>
#include<cmath>
#include<vector>

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;
    }

    // 初期値の設定
    d[0] = 0;

    while(1)
    {
        minv = INFTY;
        // 次に移動するべき頂点
        u = -1;

        for(int i = 0; i < n; i++)
        {
            if( minv > d[i] && color[i] != BLACK )
            {
                // 未訪問の頂点の中で, 最小のコストを持つ辺を探索する
                u = i;
                minv = d[i];
            }
        }

        if( u == -1 )
        {
            // 最初全域木が完成した
            break;
        }

        color[u] = BLACK;

        for(int v = 0; v < n; v++)
        {
            if( color[v] != BLACK && M[u][v] != INFTY )
            {
                // u → v の辺の中で, 最小コストの辺のコストを記録する
                if( d[v] > M[u][v] )
                {
                    // コストの記録
                    d[v] = M[u][v];
                    // 頂点 v の親を記録する
                    p[v] = u;
                    // 訪問状態の記録
                    color[v] = GRAY;
                }
            }
        }
    }

    int sum = 0;

    for(int i = 0; i < n; i++)
    {
        if( p[i] != -1 )
        {
            // 最小コストの辺の和を求める
            sum += M[i][p[i]];
        }
    }

    return sum;
}

int main(void)
{

    cin >> n;

    for(int i = 0; i < n; i++)
    {
        for(int j = 0; j < n; j++)
        {
            int e;

            // 隣接行列の設定
            cin >> e;

            M[i][j] = ( e == -1 ) ? INFTY : e;
        }
    }

    // 結果の表示
    cout << prim() << endl;

    return 0;

}

C++: #include<iostream>
using namespace std;
static const int MAX = 100;
static const int INF = (1 << 21);
static const int BLACK = 2;
static const int WHITE = 0;
static const int GLAY = 1;

int n, M[MAX][MAX];

int prim(){
	int d[MAX], p[MAX], color[MAX];
	for (int i = 0; i < n; i++){
		d[i] = INF;
		p[i] = -1;
		color[i] = WHITE;
	}
	d[0] = 0;
	while (1){
		int u = -1;
		int minv = INF;
		for (int v = 0; v < n; v++){
			if (minv > d[v] && color[v] != BLACK){
				minv = d[v];
				u = v;
			}
		}
		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] = GLAY;
				}
			}
		}
	}
	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;
	int e;
	for (int i = 0; i < n; i++){
		for (int j = 0; j < n; j++){
			cin >> e;
			M[i][j] = (e == -1) ? INF : e;
		}
	}
	cout << prim() << endl;
}

C++: #include <iostream>
#include <vector>
#include <algorithm>

class Side {
public:
	int r, l;
	int w;
	Side(int right, int left, int weight) {
		r = right;
		l = left;
		w = weight;
	};
	bool operator>=(Side s) {
		return w >= s.w;
	}
	bool operator<(Side s) {
		return w < s.w;
	}
};

class Node {
public:
	int p; /// parent
	int d; /// depth
	Node() {
		p = -1;
		d = 1;
	}
};

int Find(std::vector<Node> n, int i) {
	int a = i;
	while (1) {
		if (n[a].p == -1) return a;
		a = n[a].p;
	}
}

bool Union(std::vector<Node> &n, int i, int j) {
	int a = Find(n, i);
	int b = Find(n, j);
	if (a == b) return false;
	if (n[a].d <= n[b].d) {
		n[b].p = a;
		n[a].d = n[b].d + 1;
	}
	else {
		n[a].p = b;
		n[b].d = n[a].d + 1;
	}
	return true;
}

int main() {
	int n;
	std::cin >> n;
	std::vector<Side> side;
	std::vector<Node> node(n);

	for (int i = 0; i < n; i++) {
		for (int j = 0; j < n; j++) {
			int a;
			std::cin >> a;
			if (a != -1) {
				side.push_back(Side(i, j, a));
			}
		}
	}

	std::sort(side.begin(), side.end());
	int m = side.size();
	int cnt = 0;
	int weight = 0;


	for (int i = 0; i < m; i++) {
		if (Union(node, side[i].r, side[i].l)) {
			cnt++;
			weight += side[i].w;
		}
		if (cnt == n - 1) break;
	}

	std::cout << weight << std::endl;
}